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MSX GROUND OPERATIONS

MSX Ground Operations

James F. Smola, Michael H. Barbagallo, Joan H. Cranmer, Christoper C. DeBoy, Mark J.Harold, Julie A. Krein, Harry M. Kreitz, Jr., Albert C. Sadilek, and Harry K. Utterback

he multidisciplinary nature of ground operations necessitates careful planningfrom the start of any space program. For the Midcourse Space Experiment, groundoperations began at APL with integration and test and continued at the NASAGoddard Space Flight Center with environmental and system-level electrical testing.Mission operations simulations were conducted at every opportunity. The spacecraftand its ground support equipment were then flown to Vandenberg Air Force Base,where additional testing and simulations were conducted and the spacecraft wasprepared for launch.

T

INTRODUCTIONThe Midcourse Space Experiment (MSX) ground

operations began with the installation of the spacecraftelectrical harness on the payload adapter in mid-December 1991 and will end when the command toinitiate first-stage ignition is sent from Vandenberg AirForce Base (VAFB), California. This article discussesthe numerous steps required to get MSX integrated,tested, transported, and processed for launch during thefinal phase of spacecraft development known as groundoperations.

The assembly of the MSX structural system beganon 20 April 1992 in the APL Spacecraft Integrationand Test Area—a clean room in compliance with MSXrequirements. The structure provided a foundation forthe installation, over 2 years, of the electronics and

JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 17, NUMBER 2 (1

instruments to be flown on MSX. During integration,the electrical ground support equipment (GSE), to beused for testing and spacecraft operation, was trans-ferred from the laboratories where it was developed tothe Payload Control Center at APL, where it wasconsolidated into a fully integrated operational systemcalled the Ground Support System. In parallel, soft-ware engineers continued to fine-tune the ground andflight test software as well as the mission operationssoftware.

Environmental testing was conducted at the NASAGoddard Space Flight Center (GSFC). MSX residedat the GSFC Environmental Test Facility from 22June through 19 September 1994. There, it was dem-onstrated that MSX could withstand the acoustic and

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pyro-shock environments of the launch phase and thethermal-vacuum environment in orbit.

Transporting MSX and its GSE from APL to GSFCand then to VAFB involved moving many large piecesof equipment over land and by air under tight con-straints of temperature and daylight time. Finding aplace to process MSX at VAFB was difficult because ithad few facilities certified for hazardous operationsavailable to meet the needs of MSX. An early attemptto alleviate this problem was the construction of aPayload Processing Facility (PPF) by Astrotech SpaceOperations near the Delta II launch pad. The VAFBPayload Control Center, where the Ground SupportSystem was located, and the MSX Program Office wereset up in a NASA facility much farther away.

NASA/Kennedy Space Center/Vandenberg LaunchSite, representing NASA interests at VAFB, and theU.S. Air Force 30th Space Wing communicationssquadron played major roles in setting up the commu-nications system to support MSX operations at VAFB.In addition, APL engineers were involved in setting upthe communication links between the Payload ControlCenter and the PPF and other nerve centers vital toMSX operations.

The goal of MSX ground operations was to launcha completely tested, operable spacecraft into an Earthorbit defined by the MSX mission. The primary objec-tives were to demonstrate that spacecraft performanceand design requirements were consistent with oneanother, to show that the software designed to operateMSX in orbit was compatible with the requirements ofthe mission, and to give the mission operations teamample opportunity to develop the skills needed tooperate MSX properly.

Ground operations for MSX addressed concernsabout contamination, security, safety, and performance.Hazardous operations, particularly those involving thehandling and transfer of substantial quantities of cryo-genic substances for the Spatial Infrared Imaging Tele-scope III (SPIRIT III), were of the most serious natureof any space program managed by APL. The require-ment for 2000 L of liquid H2 made cryogenic operationsa highly scrutinized activity at VAFB.

CONTAMINATION CONTROLMost of the instruments aboard MSX are optical

sensors extremely sensitive to contamination. For ex-ample, 17 items were continuously purged with theboil-off from 440-L dewars of liquid N2. The quantityof liquid N2 consumed increased daily, peaking at 205L/day, as the instruments and special packages thatrequired purging were added to the spacecraft. Control-ling contamination at the system level was handled inthe conventional manner: a Class 10,0001 (no greaterthan 10,000 airborne particles/ft3, 0.5 mm or larger in

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size) or better clean room; complete clean room attireincluding face masks, boots, latex gloves, and tapedwrists; frequent wipe-downs of the spacecraft; weeklywipe-downs of the clean room walls; daily floor mop-pings; double-bagging of the spacecraft when the threatof contamination increased; and constant monitoringof air quality and surface contamination with particlecounters, tape lifts, and blacklight inspections.

The diverse sensor complement of MSX made con-tamination control quite challenging. Since sensor per-formance is sensitive to scatter and stray light, it wouldbe degraded by particulate contamination. The Ultra-violet and Visible Imagers and Spectrographic Imagers(UVISI) instrument was also sensitive to hydrocarboncontamination. Because of these sensitivities, contam-ination control requirements for the entire payloadwere set at the most sensitive levels: less than 10.76 mg/m2 hydrocarbon level and Level 100 particulate con-tamination for internal optical surfaces (see Table 1).To maintain the Level 100 or better on orbit, exteriorsurfaces could be no worse than Level 500 on orbit afterlaunch fallout from the launch vehicle fairing (partic-ulate that shakes free from the interior surfaces of thelaunch fairing). Allowing for this fallout, the flighthardware was maintained at no greater than Level 300during integration. When qualitative observation fromtape-lift samples indicated contamination in excess ofthis level, operations in progress were interrupted forcleaning. This process was repeated until the specifiedcleanliness level was demonstrated.

The same clean room practices were employedwherever the spacecraft was processed. The launch padwas to be the most difficult area to manage. There, thegarment dressing room is located on level 3, two levelsbeneath the spacecraft white room on level 5, and anelevator—a notorious particulate carrier—is used to getto the working levels. The local wind conditions rangefrom high velocity–sustained to extremely gusty, andthe space for personnel to work around the spacecraftis extremely limited because of all of the equipmentlocated on level 5 to support SPIRIT III cryogenicservicing.

CRYOGENICSCryogenics played a leading role during MSX ground

operations because of the special needs of SPIRIT III,the primary instrument. Since SPIRIT III is an infraredsensor, many of the optical and electro-optical elementsinside the telescope had to be cooled to cryogenic tem-peratures—nominally 10 K—to function properly andto prevent self-contamination. This cooling was ac-complished with a variety of cryogenic liquids: N2, Ar,and He, as well as Ar and H2 for flight, which werefrozen solid with liquid He during prelaunch processing.Furthermore, this ultracold condition had to be main-

NS HOPKINS APL TECHNICAL DIGEST, VOLUME 17, NUMBER 2 (1996)

tained without interruption from the moment SPIRITIII was installed in the spacecraft until launch. This feattook a large quantity of specialized equipment, skilledpersonnel working three shifts, and copious amounts ofcryogens drawn from 500-L dewar storage containers,not to mention countless industrial-sized containers ofcompressed He and N2. Liquid He was always in greatdemand and was the most difficult to obtain in the largequantities that SPIRIT III required.

Venting the boil-off of all cryogens harmlessly re-quired large amounts of cryohose interface hardwarethat had to be designed, fabricated, installed, andchecked out in time to support spacecraft operations.This requirement applied to operations at APL, GSFC,and VAFB, as well as those aboard the military aircraftthat transported the spacecraft from the East Coast toVAFB.

LOGISTICSTransporting the entire MSX cargo, including the

spacecraft and its shipping container, as well as theGSE, required five 12.2-m Flexivan trailers and a sixthtrailer used to transport noncritical hardware overlandto VAFB. Two C-5 air cargo carriers provided by theU.S. Air Force Air Mobility Command were needed forthe flight to VAFB. Travel by air was complicated bythe liquid He required to keep the SPIRIT III telescopeat cryogenic temperatures and the liquid N2 needed forpurging the contamination-sensitive instruments withN2 gas. For safety, boiled-off He was externally vented,whereas the N2 was vented into the aircraft’s cargo bay,where the accumulation was constantly monitored.Representatives of APL, Wright-Patterson AFB, An-drews AFB, Dover AFB, and VAFB met often to resolvenumerous issues before the MSX cargo was transportedto VAFB.3

SAFETYSafety issues required constant attention because of

the numerous hazardous items on MSX, including

Table 1. Surface particulate cleanliness levels(particles/0.093 m2).

Particulate size (mm) Level 100 Level 300 Level 500≥ 15 265 NA NA≥ 25 78 7450 NA≥ 50 11 1020 11,800≥ 100 1 95 1100≥ 250 NA 2 26≥ 500 NA NA 1

Note: Data are from Ref. 2.



lasers, RF transmitters and radiators, pyrotechnics,high-voltage circuits, cryogens (especially H2), radioac-tive coatings, pressure vessels, and reference objectejectors. These items were involved in various hazard-ous activities such as spacecraft handling, large packageinstallations, cryogenic operations, liquid H2 transfer,pyrotechnic checkout, and spacecraft functional/elec-trical testing.

MSX operational safety documents described therequirements for all locations, taking into account theunique operations of each site. There was the MSXEmergency Action Plan for APL,4 MSX Ground SafetyPlan for operations at GSFC5 and VAFB,6 and SPIRITIII Operational Review for Payload Processing Facility andSLC-2W.7

Since the hazards of H2 operations were of constantconcern, they were performed only at VAFB. A majorissue was how to detect a dangerous accumulation ofleaked H2 in time to evacuate personnel and preventdamage to the spacecraft and facility. To address thisproblem, two H2 sensors were mounted between theroof and the clean room ceiling of the PPF. Thesesensors were augmented by seven others positioned atstrategic locations along the liquid H2 transfer line andnear MSX. The seven sensors were selected from anine-sensor H2 monitoring system developed by Mc-Donnell Douglas for the launch pad. This system in-cluded provisions for remotely monitoring and record-ing the sensor output in the event of an evacuation.

Since VAFB mandated the remote monitoring ofsome H2 sensors, a video camera was set up so that thereadout of the two ceiling sensors could be monitoredfrom the Payload Control Center. An end-to-end testof the detection system demonstrated automatic acti-vation and power shutdown, the actuation of a roof-level exhaust louver and alarm lights (the louver opensautomatically to allow leaked H2 trapped under the roofto escape harmlessly into the atmosphere), and thenotification of the fire department.

When the SPIRIT III cryostat suffered its first inter-nal failure, the portion of the warning system down-stream of the hydrogen detection system performedsuccessfully following manual actuation. The failureresulted in the total boil-off of all of the hydrogen (64kg), which exited safely and without incident throughthe emergency vent stack. Since no hydrogen escapedinto the clean room, the hydrogen sensors were notactivated.

Safety training was compulsory for all personnelrequiring access to the various spacecraft sites. For theAPL clean room, the GSFC space environment simu-lator, and the PPF, access was granted through a card-reader badge system upon completion of safety training.Furthermore, adherence to approved, written proce-dures was mandatory for all operations at GSFC andVAFB involving the flight hardware.

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COMMUNICATIONSCommunications associated with ground operations

encompassed a variety of networks that connected thespacecraft to the Payload Control Center at a specifictest site; to the Command Center at the Air MaterielCommand’s Detachment 2/Space and Missile Center,Onizuka AFB, California; or to the Mission ControlCenter at APL. Communication links to support MSXoperations while the spacecraft was at APL or GSFCwere relatively simple. The networks at VAFB (Fig. 1),however, were quite intricate and required considerabletime to implement.

Both land-line and RF links were established forMSX operations. The land lines, consisting of bothfiber-optic and copper conductors, were set up to sup-port baseband testing. Frequent use of open-loop test-ing at VAFB is discouraged in the S-band frequencydomain, in particular, because S-band frequencies arein great demand daily. RF communications are allowedbut have time-of-day usage restrictions and requirepermission to use. Occasional RF testing is necessary toverify that MSX can communicate successfully throughthe entire RF system, including the antennas. Thisrequirement is particularly important during the hoursjust before liftoff during a last-chance confirmation thatthe communications are viable.

Communication links at VAFB were complicated bythe fact that while MSX would be located at either thePPF or a few kilometers further north at the Delta II

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launch pad, the Payload Control Center was located aconsiderable distance away at NASA Building 836.The only existing links to the PPF were several pairsof 40-year-old copper conductors of dubious quality. Tosupport MSX testing, multiple digital (up to 5 Mbps)and analog channels were needed, as was a set of point-to-point RF links (L-, S-, and X-band) from the PPFto the Payload Control Center.

The existing copper conductor pairs were capable ofproviding the necessary voice networks, telephonelines, and two low-rate data modem links to the PPF.In addition, the PPF was practically in-line with thePayload Control Center and NASA Building 1610,which already had point-to-point RF links betweenthem. To satisfy MSX RF requirements, AstrotechSpace Operations installed the appropriate antennasand cabling at the PPF. Antenna alignments and systemperformance tests were conducted by NASA RFengineers.

Many high-quality, high-data-rate, baseband (non-RF) channels were needed between the PPF and thePayload Control Center. Since VAFB could not guar-antee when the fiber-optic backbone would reach thePPF, a direct hookup to the existing VAFB communi-cations network was made via a small switching build-ing (Hut 1) about 8 km from the PPF. Since this wasconsidered MSX-unique, cost became a driving factor,so an 8-km armored fiber-optic cable was laid over theground from the PPF to Hut 1. With 10 fibers in the

Space and Missile Center,Onizuka AFB

Payload ProcessingFacility, VAFB

Launchpad Payload Control Center,

VAFB

APL MissionControl Center

16-kbps, 1-Mbpstelemetry and commands

Communicationshut

5-Mbps telemetry

Video channels

CommunicationsSwitching Center,

VAFB

APL-installedfiber cable

Voice networks, phone and

modem lines

(Existing copper pairs)

L-, S-, X-bandRF links

Payload ControlCenter

NASA GSFC

Voice networks

Satellite T1 link 16-kbps and 1-Mbps telemetry 4.8-kbps commands 3 secure voice channels 112-kbps file transfer 64-kbps Group 4 faxVo

ice n

etwor

ks

Satell

ite T

1 lin

k

Voice networks, phone and

modem lines, v

ideo channels

(Existing lines)

Voicenetworks,phone andmodemlines,videochannels(Existingfiber)

SatelliteT1 link

Commercial fax line

64-kbps data line for telemetry

and commands

(Existing VAFB fiber)

L-,S-, X-bandRF links

C-band RF data link

Voicenetworks

Figure 1 . MSX communications networks for ground operations.


cable, all of the analog, digital, and video links couldthen be sent via Hut 1 to the main VAFB Data TransferCenter and from there over the many available fibersand copper lines running to the Payload Control Cen-ter. With approval from VAFB, the fiber-cable endequipment was installed, and the completed links weretested and verified as operational in August 1994—about a month before MSX arrived. Links to otherfacilities, such as the launch pad, Onizuka AFB, andAPL, used existing communication lines.

Once the communications system was installed, asignificant effort was expended to make it fault-free.Persistent power outages at VAFB demanded that un-interruptable power supplies be placed at each point inthe baseband system (Hut 1 and the Data TransferCenter). In addition, despite labeling, an occasionaldisconnection in the Data Transfer Center intercon-nection patches would occur, breaking the link. On oneoccasion, landscapers accidentally damaged the land-laid fiber cable in two places with powered weed trim-mers. Field splices had to be made to re-establish thelink.

More serious problems surfaced with the T1 datalinks between VAFB and the Mission Control Centerat APL. A T1 link is a 1.544-Mbps full duplex data linkthat uses time-division multiplexing to relay any num-ber of lower-rate data streams between sites, providedthe combined data rates, including overhead, do notexceed 1.544 Mbps. MSX used T1 links to transfer the1-Mbps compressed science, 16-kbps telemetry, and4.8-kbps command data streams. At one point duringtesting, four T1 links were needed to communicatedigital data between VAFB and the Mission ControlCenter. Jitter introduced in each T1 link multiplexercontributed to frequent clock slips (analogous to biterrors, where a bit is dropped from the data streamentirely instead of being misdetected). This problemwas particularly evident in the 1-Mbps science datalink, where the jitter from the multiplexer was a largerfraction of the clock cycle and led to unacceptably highbit-error rates. For this channel, it was possible tobypass the two T1 links at VAFB by transmitting thedata over video lines and regenerating a clean clockwith a bit synchronizer. This change removed half ofthe jitter contribution from the total T1 link, and theerror rate improved.

The initial performance verification and debugging(shakedown) of the MSX communication system atVAFB included the linking of the Vandenberg TrackingStation east of the PPF as well as the Space and MissileCenter at Onizuka AFB. At one point during the pro-cessing, a fully equipped, portable ground station calledthe Transportable Space Test Resource, provided by theSpace and Missile Center, was parked alongside the PPFto communicate with the MSX inside to demonstrate



that the Space and Missile Center would be able tocommunicate with the orbiting MSX successfully.

Much later, after the second cryostat failure, thePayload Control Center had to be moved to a triple-wide trailer near the PPF. Although the closer proxim-ity to the PPF provided many advantages, the connec-tivity between the original Payload Control Center andthe MSX communications network already in place atVAFB had to be shifted to the new Payload ControlCenter. This matter was further aggravated by the un-certainty of the extension of the VAFB fiber-opticbackbone to the PPF. Overall, however, the MSX com-munications networks at VAFB worked extremely well.

SECURITYAPL was responsible for MSX security planning,

coordination, and oversight at all APL locations,GSFC, and VAFB. The Laboratory was also responsiblefor protecting the integrity of the MSX spacecraft,GSE, and mission operations, which included theMission Control Center, Mission Processing Center,and Operations Planning Center, as well as the datamanagement at all of these centers.

To protect MSX and its sensitive mission objectives,the MSX Program Protection Plan8,9 was developed. Acard-reader system, an armed guard, or both, were usedat every facility in which MSX or its GSE were residentto prevent unauthorized entry into either the spacecraftroom or the control center(s). Alarms or warning lightswere installed in strategic places to alert the guards ofillegal entries. For the off-hours, door-mounted combi-nation locks were added for extra protection. Lockcombinations were revealed to only a few people. Videosurveillance was provided at the entry points to allsecurity-sensitive areas at APL. Communications secu-rity equipment mounted on MSX and in GSE racks waskept secure with metal cage locks and visual or videomonitoring.

PERFORMANCE ASSURANCEPerformance assurance concerns itself with the dis-

ciplines of reliability engineering, quality assurance,and systems safety. Its role during spacecraft processingwas governed by the MSX Product Assurance Plan.10

Other performance assurance documents are listed asfollows:

• Integrated Test Specification for Space Payload Equip-ment11

• Technical Services Department Hardware ConfigurationManagement Manual12

• MSX Program Test Plan13

• Various acceptance test procedures• Automated computer test scripts (runstates)

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The performance assurance engineer is responsiblefor controlling and documenting all of the variablesaffecting reliability, quality, and safety once integrationbegins. This job at the system level is largely a contin-uation of the earlier package-level (individual electron-ic module) effort but with a significant adjustment inperspective. Concern over package quality and perfor-mance carries over to the system level, broadening toconsider the interdependency of all packages and theirperformances as parts of a much larger and more com-plex system.

For the integration and test phase of MSX, the maintasks of the performance assurance engineer includedthe verification that the subsystem was ready to inte-grate; maintenance of the problem/failure reportingsystem as well as tracking the corrective actions; mon-itoring conformance with the program test plan; andpreparing monthly reports to the MSX Program Officeon the condition of the spacecraft and operations as-sociated with its processing.

Performance assurance received close attention onMSX. The spacecraft is extremely complex and theoperating system consists of numerous electronics pack-ages, many of which are populated with large quantitiesof densely packed electrical connectors. The total con-nector count for MSX, not including internal packageconnectors, is 1547; more than half of these are in theprimary, redundantly wired electrical harness thatweighs 163 kg.

Numbers and types of connectors became an impor-tant aspect of integration and test since many packageswere integrated more than once. Connections and dis-connections became so numerous in some cases thatconnector pin wear and damage had to be closelymonitored.

INSTRUMENT PURGINGA purge system was integrated into MSX to contin-

uously provide the contamination-sensitive instru-ments with research-grade (99.9995% pure) N2 gasfrom the time of installation until liftoff. Instrumentinternal pressure was maintained at more than 0.266kPa (2 torr) above atmospheric, with a design goal of0.665 kPa, to prevent the entrance of contaminants.Once the system was in full use, it was discovered thatsome of the instrument housings were not as leak-tightas expected. To compensate for excessive leakage, thepurge-gas flow rate was elevated from the 77 L/mindesign criterion to 99 L/min to maintain the minimumpressure differential of 0.266 kPa in the instrumenthousings with the largest leaks.

Purge gas was distributed to the instruments via a U-shaped stainless steel manifold wrapped around thebottom of the instrument section. The lines that con-nected each instrument to the manifold were provided

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with flow restrictors to meter the gas. Pressure in themanifold was set at 99.98 kPa, so the flow through therestrictor was sonic (choke flow), which provided aconstant-volume gas flow to each instrument, regard-less of other users of the manifold.

The purge manifold had a primary inlet used forroutine ground purging and an inlet with a flyawayfitting that disconnected when the umbilical towerretracted. The flyaway feature allowed the purge tocontinue right up to liftoff. Check valves in all hoseconnections sealed disconnected lines to stop purge-gasbackflow and prevent contaminants from entering themanifold.

The MSX purge-gas monitor suitcase contained gasregulation, analysis, and filtration equipment. Inlet gasin the 689.5- to 861.8-kPa pressure range was regulateddown to the 99.98- to 110.3-kPa range to feed theconnecting hoses and spacecraft manifold. An elec-tronic hygrometer in the suitcase was programmed toconstantly monitor the N2 purge-gas pressure, temper-ature, and H2O and O2 content to verify its purity. Anout-of-range indication of any of these parameterswould activate a flashing amber alarm light and a tele-phone auto-dialer that would alert service personnel.

The need for continuous purging required a portableliquid N2 supply any time MSX had to be moved fromone facility to another. Three leased, pristine dewarstorage containers, equipped with built-in pressurebuilding and evaporator coils and filled with liquid N2,were shipped along with the spacecraft when it wastransported between facilities. Two of them were 440-L containers, each providing a 52-h supply; together,they were adequate for all planned trips, including theone to VAFB on the C-5 air cargo carrier. A 160-Ldewar provided an 18-h reserve of liquid N2 in case ofan emergency and for use on the McDonnell Douglashandling cart for transporting MSX from the PPF to thelaunch pad.

For air transport, provisions were included to dumpN2 overboard through a special bulkhead attached tothe C-5’s fuselage to avoid filling the cargo bay withoxygen-depleting nitrogen in the event of a catastroph-ic release from either dewar.

INTERFACING WITH CRYOGENICSYSTEMS

Cryogenic interfaces were required between theSPIRIT III GSE and the various test/processing facil-ities. They were also required between MSX and itssupport hardware such as the shipping container/trans-porter and C-5 air cargo carrier. All SPIRIT III cryo-genic servicing equipment, with interfaces liberally dis-tributed throughout, was strategically positionedaround MSX. Much of it was connected to SPIRIT IIIwith vacuum-jacketed hoses. To minimize the loss of


cryogen through boil-off during transfer operations, thehoses were kept as short as possible. Typical lengths fellin the range of 4.6 to 7.6 m.

In addition, the shipping container was equippedwith cryogenic bulkhead fittings for the emergencyvent as well as the cryostat, aperture door, and orbitvent. Also, two ports in the GSFC space environmentsimulator were modified to accept bayonet bulkheadfittings so that SPIRIT III and the other instrumentscould be serviced in the chamber by cryogenic GSElocated outside the chamber. A pressure-relief systemwas installed in the C-5 aircraft to protect SPIRIT III’sinternal burst disk system from sizable pressure differ-entials that would be experienced at high altitude.

At the PPF, SPIRIT III was loaded with liquid H2from a 1000-L dewar located outdoors for safety rea-sons. An identical dewar, also filled with liquid H2 forthe gas top-off, and a 440-L dewar of liquid N2 for theinstrument purge were located on a concrete pad alongwith the primary dewar about 7.6 m away from thebuilding. A custom-made cryogenic bulkhead fittingwas mounted to the wall of the PPF about 4.9 m aboveground level—the height of SPIRIT III’s hydrogeninlet. This fitting helped support the 7.6-m-long insideand outside cryogenic hoses that connected SPIRIT IIIto the supply dewar outside. A specially designed,environmentally sealed panel was mounted on the wallof the PPF, to which a He vent hose and the N2 purgeline were attached. The panel also provided sealedpassages through the wall for the H2 and emergencyvent hoses. These two hoses were connected to custominterfaces on the emergency vent stack, which wasattached to the outside wall of the PPF and exhaustedabout 1.8 m above the roof top. (The PPF roof is 12.2m above ground level). A portable vent stack also wasattached to the wall of the shipping container andconnected to the SPIRIT III emergency vent port witha short piece of vacuum-jacketed hose and fitting.

Cryogenic interfaces on the launch pad are basicallythe same as those at the PPF, except for the liquid H2transfer hose. For safety reasons, H2 transfer on the padis prohibited.

SPACECRAFT AND INSTRUMENTALIGNMENTS

The SPIRIT III, UVISI, and Space-Based Visible(SBV) instruments were to be coaligned within 0.1°,including uncertainties due to mapping errors, thermaldistortion, and stress-induced distortion and hysteresis.Also, their lines of sight were to be mapped into theMSX coordinate system for boresight pointing knowl-edge. To meet these requirements, alignment errorbudgets partitioned the 0.1° between thermal distor-tions, mechanical distortions due to ground-to-orbittransitions, stress-induced distortions, and alignment



errors. Mapping and shimming alignment errors hadto be kept to less than 0.03° to meet the coalign-ment specification.

To satisfy the instrument coalignment criteria, thefollowing plan was implemented: A calibrated opticalcube was mounted on each instrument or sensor(UVISI consists of nine independent sensors), andthen the line-of-sight vector of each one was mappedinto its optical cube. After each instrument was mount-ed on the spacecraft, its optical cube orientation wasmapped with respect to the MSX coordinate system.The SPIRIT III mounting surface—the support ringaround the cryostat—was used to define the coordinatesystem. Minimizing the coalignment errors of SPIRITIII, UVISI, and SBV to this interface allows the instru-ments to keep the observable targets in their respectivefields of view simultaneously.

After the initial assembly and alignment at APL, allinstruments and attitude control devices wereremapped before and after environmental testing atGSFC and after shipment to VAFB. During the map-pings at APL and GSFC, all of the high-resolutioninstruments had an average misalignment of less than7 arcsec (0.002°). However, during the transit of MSXto VAFB, all of the instruments shifted 0.014° withrespect to spacecraft coordinate axes.14 This shiftingwas attributed to a settling of the instrument sectionat its interface with the graphite-epoxy truss. All in-struments except SPIRIT III, however, maintainedtheir relative coalignments, and the small offset rela-tive to SPIRIT III was within tolerance.

ELECTROMAGNETICENVIRONMENTS

To avoid damaging MSX electronic componentssensitive to electromagnetic radiation and to establishwhat effect the ambient RF environment might haveon electrical testing, electromagnetic surveys in andaround the PPF and level 5 of the launch pad wereconducted in September 1994.15 RF frequencies from10 kHz to 10 GHz were monitored to determine po-tential field strengths during spacecraft processing. Pre-vious radiated susceptibility tests on the transpondersystem, for example, showed that direct radiationscould disturb this system’s operation in the 200- to1000-MHz range at field strengths of 1 to 2 V/m. Otherradiated susceptibility tests involving the integratedspacecraft at APL demonstrated that MSX could with-stand field strengths as high as 10 V/m at specific fre-quencies that occur at VAFB at certain times. Never-theless, other signal frequencies that could causedisruptions at lower field strengths might be present.

Previous RF surveys conducted during the fall of1993 and summer of 1994 at the launch pad and thePPF showed that known tracking radars as well as

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surveillance radars could impinge on these locationswith high levels (>10 V/m) of RF interference. Specialcontrols were instituted to keep this from happeningwhile MSX resided at VAFB.

The electromagnetic survey indicated a slightchance that MSX would encounter a radiated suscep-tibility problem at VAFB. It showed that MSX hadimmunity of up to 1 or 2 V/m across the entire spec-trum. Although the survey was comprehensive, it cov-ered only the common types of electromagnetic inter-ference emissions at VAFB. It did not guarantee thatsomething disruptive would not occur.

VITAL SUPPORT FUNCTIONSThe daily spacecraft maintenance routines included

flight battery conditioning and instrument purging(discussed earlier). Documentation consisted of 80electrical, mechanical, environmental, and mission-related plans generated to meet the requirements of theMSX Program Test Plan.13 In addition, numerous doc-uments covered contamination control, communica-tions, safety, security, and logistics support operations.

Photo-documentation provided a visual and chron-ological record of all spacecraft activities from thebeginning of integration until liftoff. These photo-graphs were archived in the APL MSX ProgramOffice and were invaluable to MSX engineers duringreintegration.

SUBSYSTEM INTEGRATION:EVOLUTION OF MSX

The object of subsystem integration is to verify thatthe subsystem being integrated is compatible, both me-chanically and electrically, with the previously inte-grated subsystems and to check the subsystem for func-tional performance. Integration is a prelude to the morecomprehensive system-level tests discussed later in thisarticle.

Before integration, all subsystems had to meet theapplicable pre-integration flight acceptance require-ments. The performance assurance engineer document-ed departures from requirements and alerted the APLMSX Program Office. If a problem could not be re-solved quickly, a “workaround” was devised to preventdelay of integration. The final step before subsystemintegration was the integration readiness review, wherethe subsystem’s lead engineer demonstrated the sub-system’s readiness to other APL MSX engineers.

Subsystem integration began with the delivery of thepackage(s) to MSX for pre-installation resistance mea-surements. Next, the delivered unit or units were in-stalled at the proper locations on MSX, power andsignal connectors were mated, units were powered up,and signal interfaces were checked. The final check wasan “aliveness test”: a relatively simple functional test

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that verifies whether or not the circuitry within thepackage is working properly at nominal voltage underambient conditions.

Throughout integration, functional test proceduresand computer test scripts called “runstates” enabled thetest conductor and test team to verify quickly whetherthe subsystem being integrated was functioning prop-erly and was compatible with the other subsystemsalready on MSX. Interface compatibility between thesubsystem GSE and the Ground Support System wasestablished earlier.

SOFTWARE TESTINGWhile MSX was under development and well into

the integration and test phase, the complex softwareneeded to operate MSX during ground testing and inorbit was being developed. The effort was segmentedinto 16 areas covering the various spacecraft subsystemsand mission operations.

Software testing16 was done in four phases: (1) unittesting, (2) module integration testing, (3) verificationtesting, and (4) acceptance testing. Unit testing veri-fied that the program unit performed as specified in thedesign documents. Module integration testing followedsuccessful unit testing and integration of the units intoa subsystem. This process continued until the entirepackage of units was integrated into a system (module)and was ready for verification. After module integrationtesting indicated that the software performed as spec-ified in the design documents, verification testing wasconducted.

Verification testing was done in accordance with thesoftware requirements documents and involved targetcomputers and attendant hardware on MSX. The soft-ware was verified by the APL-developed attitude pro-cessor/tracking processor (AP/TP) testbed simulatorwhenever spacecraft instruments were not available.The AP/TP testbed simulator played a central roleduring the integration of the various flight processors.

Acceptance testing was conducted throughout inte-gration and test. Mission profiles were run in conjunc-tion with specific tests to verify that the latest hardwareor software modification did not somehow “break” thesoftware. All software testing was documented in thesoftware engineering logbook, kept in the AP/TP test-bed simulator as an electronic record, or was recordedchronologically in handwritten notes. The AP/TP test-bed simulator was a frequent stand-in for missing hard-ware during this phase. Stress testing was performed onthe AP/TP testbed simulator, in parallel with continuedspacecraft testing, to verify the robustness of the soft-ware. Throughout acceptance testing, operator hand-books were compiled so that mission operations person-nel could have documents based on “real-life”experience to refer to when operating MSX.


PRELIMINARY HARDWARE/SOFTWARE TESTING

The attitude, tracking, and image processors weresubjected to initialization, data handling system, mem-ory dump, and real-time commanding tests during theinitial phases of spacecraft integration. In addition, thetracking processor, in conjunction with UVISI, SBV,the beacon receiver, and the attitude processor, partic-ipated in pointing verification tests.

Attitude processor pointing verification includedtests to demonstrate magnetic and gravity gradient mo-mentum dumping. Real-time commanding by the atti-tude processor involved the X-band antenna gimbal,the solar array drive, and magnetic torque rods. TheUVISI image processor was tested to verify the trackingmessage, imager input, and image processing control.

Systems tests consisted of simulated track scenariosusing data from the beacon receiver and UVISI. Errorswere introduced deliberately to demonstrate how wellthe software would deal with spurious out-of-range andconflicting data as well as data dropouts. Systems testsof this nature were performed on the AP/TP testbedsimulator to verify, once again, that the software wasrobust.

INTEGRATION AND TESTFor a large and complex spacecraft, integration and

test is a process that, by its very nature, threatens to goon forever. For MSX, it was the most time-consumingand mentally challenging activity of all.

By early June 1992, the entire structural system,consisting of the instrument section, the electronicssection, and a graphite-epoxy truss connecting the two,was fully assembled. Over the next 2 years, all of theother elements were integrated. To identify interfaceincompatibilities promptly, some elements of all of theinstruments were installed at the forward end of theinstrument section.

The instrument section provided structural connec-tivity for the beacon receiver antenna array and theoptical bench, to which was mounted the star cameraand ring laser gyros for attitude control and detection.The horizon sensors and several DSADs for the attitudecontrol system were also mounted on the instrumentsection. Reference object ejectors were assembled to apair of half-panels that were then installed on theforward end of the instrument section. A significantportion of all electrical testing was done with MSX inthis configuration.

At the end of April 1994, the SBV sensor, referenceobject ejectors, optical bench, and beacon receiverantenna array were temporarily removed from the in-strument section so that the SPIRIT III sensor couldbe installed. A major milestone was reached with theinstallation of the SPIRIT III sensor on 9 May 1994.



During May and June 1994, the integration of UVISIwas completed.

At this point, a meaningful, system-wide alignmentcheck of the instruments and attitude sensors could bemade. In addition, MSX was now configured for thecomprehensive baseline performance test.

BASELINE PERFORMANCE TESTThe baseline performance test comprised four parts:

(1) the spacecraft functional test, (2) the spacecraftperformance test, (3) special tests, and (4) missionsimulation. One baseline performance test was run atAPL before MSX was shipped to GSFC for environ-mental testing, two were run at GSFC during thethermal-vacuum test, and another was run at VAFBduring spacecraft processing.

The spacecraft functional test verified that the sys-tem operated properly, i.e., that the subsystems inter-acted as expected. This was a nominal condition testthat did not subject MSX to a wide range of conditionsfor performance assessment. The spacecraft perfor-mance test, on the other hand, was designed to verifyperformance specifications. Of much longer duration,it tested MSX to extremes under a wide range of sce-narios designed to simulate on-orbit conditions. Thespacecraft functional test took slightly more than 1 dayto complete, whereas the spacecraft performance testtook about 4 days.

Certain performance tests had to be conducted in-dividually for reasons of practicality. For MSX, 26 ofthese special tests were done.

Mission simulation was a ground-based “orbitalshakedown” during which MSX was subjected to ex-tremely harsh conditions analogous to the most stressfulit would experience in orbit. It consisted of two parked-mode orbits followed by a target track simulation andfive additional parked-mode orbits. Included werespacecraft downlink events, such as the 25-Mbps primescience, 1-Mbps wideband, and 16-kbps housekeepingdata. Command messages at 2 kbps were generated anduplinked to the spacecraft command receiver. In everyinstance, command execution was verified.

During testing, the mission operations team, toenhance its proficiency, was given ample opportunityto control the spacecraft. During these periods, thepayload test team performed routine tasks and operatedin a standby mode, ready to assume control of MSX ifa problem occurred.

ENVIRONMENTAL QUALIFICATIONOn 21 June 1994, the Test Interfaces and Require-

ments Document (TIRDOC)17 was jointly approved byAPL and GSFC and distributed in final form, after 3years of coordination between engineers of both orga-

996) 181

J. F. SMOLA ET AL.

nizations. On that same day, MSX and all of its GSwere shipped to GSFC for environmental testing. MSactivities at GSFC began on 22 June 1994, in complance with the TIRDOC, and continued until 19 Setember 1994, when MSX and all of its mechanical ancryo-handling GSE were shipped to Andrews AFB fthe journey to VAFB.

For environmental qualification, MSX was removefrom its shipping container at GSFC, installed onsupport structure called the “elephant stand,” antransported on air bearings to the Spacecraft SystemDevelopment and Integration Facility clean roomOperations in the clean room concentrated on prepaing MSX for instrument alignment checks, acoustsimulations, pyro-shock tests, and thermal-vacuutests in the space environment simulator. Figure shows engineers and technicians installing the SPIRIIII sunshade on MSX.

Instrument alignment was checked before and afttransit to GSFC and after environmental testing. good correlation of results provided confidence in thperformance of the instruments and attitude detector

While accelerometers and thermocouples were bing installed on MSX in preparation for the acoustipyro-shock, and thermal-vacuum tests, instrumenpurging with the boil-off from liquid N2 continueuninterrupted. Likewise, the cooling of SPIRIT III witliquid He and liquid Ar also continued uninterrupteWhen the preparations were complete, MSX was diconnected from the SPIRIT IIIcryogenic GSE, double-bagged,and transferred on air bearings tothe acoustic cell for testing.

The object of the acoustic testwas to subject MSX to a simulationof the worst launch-vehicle–induced environment. The space-craft, including all thermal blan-kets, was in its launch configura-tion atop the elephant stand andthe launch vehicle payload attachfitting. All of the pyrotechnicallyactuated devices were connectedfor the pyro-shock testing that wasto follow, and the double baggingremained in place to protect thespacecraft from contamination inthe acoustic cell, which was notequipped to provide filtered air.

First, MSX was subjected toa functional test, which was repeat-ed after the acoustic test. It wasthen commanded into its launchmode just moments before theacoustic test began. Although theflight acceptance test lasted 60 s,

Figure 2 . Instalforward end of M

182

total exposure to the acoustic environment lasted about2 min. The extra time was required for acoustic inputcalibration and equalization at –6 dB. The post-testindicated that the electrical system survived the acous-tic simulation.

The pyro-shock test simulated the actual shockpulses generated by the pyrotechnic uncaging of all ofthe deployable equipment—antennas and instrumentaperture covers—and the release of the clamp bandjoining MSX via the payload adapter to the payloadattach fitting. Consistent with accepted practice, allpyro-initiated events were tested twice.

Not only did these tests provide valuable shockpropagation data, they also demonstrated the uncagingand deployment of all of the deployable elements.Another functional post-test indicated that the electri-cal system survived pyro-shock testing as well. At thispoint, MSX was ready for the final phase of testing atGSFC in the space environment simulator.

MSX thermal-vacuum testing began on 25 July 1994and ended on 22 August 1994. The 4-week test pro-gram consisted of two hot and two cold thermal balancetests, a hot and cold functional test, and a hot and coldsurvival test. Test conditions—total testing hours,number of thermal cycles, and temperature levels—were derived from the Integrated Test Specification forSpace Payload Equipment.11 The purpose of the thermal-vacuum test was to simulate orbit environments andensure proper functioning of MSX and its components.

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lation of the gold-plated sunshade around the SPIRIT III aperture cover on theSX during environmental testing at GSFC.

JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 17, NUMBER 2 (1996)

Specifically, it was designed to evaluate the following:

• Performance of the thermal and power systems in thepark mode at both full-Sun and maximum-eclipsedorbits

• Capability of the thermal control system to maintaincomponent temperatures expected during the mis-sion for the eclipsed and full-Sun orbits

• Electrical performance of the subsystems while cy-cling temperatures to the hot and cold levels specifiedin the thermal-vacuum test during the baseline per-formance test

• Capability of the thermal and power systems to sup-port target encounter missions

• Performance of the thermal control system undersurvival conditions

MSX in its orbital configuration—with thermalblankets in place but minus solar panels—was attachedto a mounting fixture in the center of the chamber.Temperature control during the thermal-vacuum testwas maintained with a GSFC-developed heater shroudformed into an irregular octagon that completely sur-rounded the spacecraft. The heater shroud was used toprovide equivalent sinks, and the chamber cold wallwas set to liquid N2 temperature (2190°C). Over 400test thermocouples were installed on MSX to monitorthe temperatures of the instruments and support systemelectronics packages. Thermocouples were placed instrategic locations to evaluate the integrity of the ther-mal design and operation of the heaters and thermo-stats, and to establish a correlation between flighttelemetry and thermocouple-measured temperatures toverify the performance of the flighttemperature sensors.

Aside from the usual startupproblems, the thermal-vacuum testran smoothly, except for one seri-ous problem. Despite all of theplanning, a subtlety of the spaceenvironment simulator surfacedafter the thermal-vacuum test be-gan. If it had not been for severalcryo-hose penetrations of thechamber’s cryo-liner (shroud), theproblem would never have beendiscovered. The cryo-hoses servedas conduits for the liquid He andliquid Ar required to maintain theSPIRIT III telescope at its opera-tional temperature during the test.A little known fact about theshroud was its proclivity to changeposition whenever liquid N2flowed through it. This conditionwas critical for MSX because noallowance was made for it in the

Figure 3 . MSX in its Andrews AFB for the

JOHNS HOPKINS APL TECHNICAL DIGEST, V


clearances between the cryo-hoses and the shroudpenetrations for them. Tests run years earlier by GSFCindicated that the shroud would “walk” far enough tocontact the cryo-hoses and subject them to sizable side-loads. These sideloads could have caused serious dam-age to the hoses or degradation in the joint seals at thechamber wall feed-through plates, resulting in leakageof liquid He or Ar into the chamber during the thermal-vacuum test. It took 5 days to correct the condition,and the delay in the schedule had to be made up later.

After completion of the thermal-vacuum test, afunctional post-test was run. Then, MSX was double-bagged, removed from the space environment simula-tor, set back down on the elephant stand, and, via airbearings, transported back to the clean room.

FINAL TESTING, PRE-SHIPPREPARATIONS, AND TRANSPORTTO VAFB

Back in the clean room, MSX was unbagged andreconnected to its cryogenic and electrical GSE. Asolar array drive test was conducted, followed by rein-stallation of the solar panels (the solar panels were notrequired for the thermal-vacuum test), alignment re-verification, cleaning, double-bagging, and final cryo-genic servicing. After that, MSX was returned to itsshipping container and, along with the remaining GSE,transported at 3:00 a.m. on 19 September 1994 toAndrews AFB for the trip to VAFB.

It took about 3 h to load MSX on the C-5 air cargocarrier (Fig. 3) provided by the U.S. Air Force Air

shipping container is being transferred to the C-5 air cargo carrier atflight to VAFB.

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Mobility Command Squadron stationed at Dover,Delaware. For logistical reasons, the Payload ControlCenter GSE was shipped 1 week ahead of MSX. Prep-arations at VAFB for the arrival of MSX were explainedor illustrated in the MSX Launch Site VAFB OperationsPlan.18 The Payload Control Center at VAFB was setup and on-line by the time MSX was cabled and readyfor functional verification at the PPF.

PAYLOAD CONTROL CENTEROPERATIONS

The Payload Control Center was the focal point forall activities related to electrical testing. The baselineperformance test, mission simulation test, exclusionzone test, concept of operations test, special functionaland subsystem tests, launch readiness tests, and launchdress rehearsals were all orchestrated from the PayloadControl Center. With the exception of a couple of RFracks, the AP/TP testbed simulator, battery monitoring/charging equipment, ground power, blockhouse controlunits, and a variety of monitoring equipment, all of theMSX GSE was located in the Payload Control Center.The exceptions were set up in the PPF control room,16 km north of the Payload Control Center and adja-cent to the PPF clean room where MSX was located.

The spacecraft systems engineer controlled activitiesat the Payload Control Center, and the program sys-tems engineer coordinated testing. The spacecraftmanager controlled activities at the PPF. Spacecraftstatus, work schedules, test schedules, and current prob-lems were discussed at daily meetings chaired by theAPL MSX Program Manager. The daily interchange oftechnical and administrative information was consid-ered essential to the success of MSX operations.

PPF OPERATIONSMost of the activity in the PPF involved mechanical

operations, including SPIRIT III cryogenic servicing;package removals and reinstallations; spacecraft han-dling, cleaning, bagging, and unbagging; instrumentalignment verification and purging; reconfiguring forspecific tests; localizing air conditioning; thermal blan-keting; scaffold assembly and repositioning; and sup-porting spacecraft electrical testing, as necessary.19

PPF activity centered on the SPIRIT III cryogenicservicing. Key to that instrument’s success was the con-stant chilling needed to maintain a high level of inter-nal cleanliness. The goal was to keep SPIRIT III at itsoperating temperature (about 10 K), which was re-quired for electrical testing. Satisfactory performance at10 K was a prerequisite to filling the cryostat with liquidH2 and freezing it for launch by circulating liquid Hethrough cooling coils wrapped around the cryostat’sinternal reservoir.

184 JOHN

Nearly all prelaunch preparations took place in thePPF clean room with MSX clamped to the Delta IIpayload attach fitting, which was bolted to a floor-anchored spacer provided by McDonnell Douglas.Before testing could start, workers had to position scaf-folding around MSX, remove the bagging, connectcryogenic and vacuum hoses to SPIRIT III, connectMSX to its GSE, and uncage the beacon receiverantenna array and rotate it into its flight position.

MISSION OPERATIONS SIMULATIONTEST

The mission operations simulation test (MOST)20

was one of several tests of the mission integrated readi-ness test, which was devised to establish the readinessof the MSX postlaunch operations teams and theworldwide network designated to support those opera-tions. The objective of MOST was to demonstrate thatthe operations teams could carry out daily integratedspacecraft control and assessment operations. MSXserved as a testbed. The object was to have the oper-ations teams interface with MSX through the Air ForceSpace Communications Network on-orbit networkconfiguration and demonstrate daily operations andcommunications for 12 h of dedicated target eventoperations and 24 h of early on-orbit operations.

Aside from the usual start-up problems and someminor anomalies that surfaced, MOST was conductedsuccessfully. It gave the operations teams ample oppor-tunity to hone their skills for operating MSX in orbit.

HYDROGEN TRANSFER ANDSOLIDIFICATION

Because excessive handling of liquid H2 is discour-aged for safety reasons, loading SPIRIT III with liquidH2 was deferred until it demonstrated acceptable elec-trical performance.21 The first step was to terminate theflow of liquid He into the cryostat’s internal reservoir.(liquid He was used to cool the reservoir for routineperformance testing and precooling before introducingliquid H2). Then, liquid H2, contained in a 1000-Ldewar located in an outdoor, limited-access area 7.6 maway from the PPF, was transferred through a largevacuum-jacketed hose connected to a special bulkheadadapter mounted to the wall. A similar hose of the samelength was connected to the other side of the sameadapter and the cryostat H2 fill port, giving the liquidH2 a continuous conduit for steady flow from the 1000-L source to the cryostat.

After about 64 kg of liquid H2 was transferred, flowof liquid He resumed through the cryostat’s coolingcoils until all of the liquid H2 in the reservoir was frozensolid. Keeping the H2 solid required liquid He circulat-ing through the cooling coils late into the prelaunch

S HOPKINS APL TECHNICAL DIGEST, VOLUME 17, NUMBER 2 (1996)

countdown. The intent was to keep the frozen H2 fromreaching the triple point (the temperature and pressureat which all three phases of a substance coexist inequilibrium) too early in orbit to give the contaminatedatmosphere surrounding MSX sufficient time to dis-perse before opening the instrument covers. Delayingthe cover openings as long as possible decreases thechance that instrument performance might be degrad-ed due to outgassing residuals from materials on MSX.Ten to fourteen days was considered optimum.

Although liquid H2 was transferred to SPIRIT IIIand solidified successfully at the PPF, an anomaly de-veloped inside the cryostat after the transfer, causinga converter to rupture and thereby terminating MSXprelaunch processing on 2 November 1994.

Solidification of the H2 was considered a majormilestone. On the day the failure occurred, MSX wasonly 16 days away from launch. SPIRIT III was subse-quently removed from MSX and shipped to the cryostatdeveloper for disassembly, inspection, and repair. It wasreturned to VAFB for reintegration with MSX on 5April 1995.

Several weeks later, with the reintegration processwell under way, the pressure in the cryostat’s vacuumspace could not be reduced to a level low enough tocontinue with the cooling-down process. This wassymptomatic of an internal leak, so the prelaunch pro-cessing was suspended again. SPIRIT III was removedfrom MSX and returned to the cryostat developer asecond time for inspection and repair.

LAUNCH PAD OPERATIONSLaunch pad operations will be-

gin well before the spacecraft ar-rives from the PPF. It will takeseveral months to get the Delta IIlaunch vehicle integrated in themobile service tower (Fig. 4) andprepared for installation of MSX.To maintain control over environ-mental quality in the spacecraftwhite room of the mobile servicetower, the cryogenic GSE and oth-er support hardware required onthe pad to service SPIRIT III willbe transferred from the PPF to themobile service tower well aheadof MSX. When MSX arrives atthe pad, all of the cryogenic GSEwill be in place and seismicallyrestrained, and the white roomenvironment will be fairly wellstabilized. The object is to limitthe exposure of the white room tothe natural environment while Figure 4 . The Delta

JOHNS HOPKINS APL TECHNICAL DIGEST, VO


MSX is being transferred into it. Having the cryogenicGSE in place will make rechilling quick and straight-forward.

MSX in its shipping container will be hoisted bygantry crane to level 5 of the mobile service tower,stripped of its outer bag, and moved into the whiteroom for the final 14 days of ground operations. Oncethe container is in the white room and positioned overthe Delta II second stage, the gantry doors will be shut.The container will then be lowered until the payloadattach fitting contacts the forward end of the Delta IIguidance compartment. After the payload attach fit-ting is bolted to the front end of the launch vehicle,the shipping container will be removed from MSX andstored in the mobile service tower.

After MSX is securely attached to the second stage,the following will occur:

• The hydrogen emergency vent line will be connectedto the SPIRIT III emergency vent and the launch pademergency vent stack.

• The installation of the launch pad hydrogen monitor-ing system will be completed.

• The MSX instrument purge manifold will be con-nected to the liquid N2 boil-off source located atground level close to the mobile service tower.

• MSX will be connected to the RF and land-linecommunication links running between the launchpad (umbilical connections) and the Payload Con-trol Center.

• The battery charging and conditioning system andbattery air conditioning will be set up.

• The clean room will be stabilized quickly to allowoperations to begin on schedule.

II launch tower overlooking the Pacific Ocean.

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J. F. SMOLA ET AL.

• Cryogenic servicing equipment will be connected tothe SPIRIT III cryostat to reestablish the frozen H2 toprevent it from reaching the triple point.

• The Ar servicing equipment will be connected to theSPIRIT III aperture door for cooling necessary toinhibit telescope contamination.

• A spacecraft functional test will be conducted.

For launch to occur by the prescribed date, the flightfairing will be assembled around MSX about 8 daysbefore launch, which is 6 days after the spacecraftarrives at the pad. Access after that will be restrictedbecause most of the areas around MSX will be inacces-sible. Large holes provided by McDonnell Douglas incritical areas of the fairing will allow access for certainoperations on the pad. Antenna hat coupler installa-tions and removals, safe plug removals, arming pluginstallations, final ordnance checks, cryogenic hoseconnections and disconnections, removal of nonflightitems, and final thermal blanket closeouts are but someof the operations to be done after the fairing is installed.To minimize contamination, the inner bag will be re-moved from MSX through the gap between fairingsections late in the fairing integration process.

During the 14 days that MSX will spend on the pad,four functional tests will be run in addition to a launchmode test, a stray voltage test, and a mock launchcountdown with the launch vehicle. Two days beforelaunch, a spacecraft readiness review will be held inconjunction with a launch site readiness review.

CONCLUSIONMuch of what falls under the general classification

of ground operations takes place in the shadow ofground operations tied directly to spacecraft process-ing. As a result, much of the planning, coordination,and implementation that occur years before processinggo largely unnoticed. Contamination control, security,safety, performance assurance, communications, envi-ronmental testing, logistics, instrument purging, cryo-genic operations, alignment verification, battery

186 JO

conditioning, electromagnetic surveys, interface coor-dination, and documentation all helped MSX to reachthe various milestones leading to its ultimate destina-tion. We hope that those unfamiliar with the detailsof ground operations now have a better understandingof what goes on behind the scenes from the first signsof integration until the words “ignition” and “liftoff”are heard.

REFERENCES1 Federal Standard Clean Room and Work Station Requirement, Controlled

Environment, FED-STD-209D (Jun 1988).2 Product Cleanliness Levels and Contamination Control Program, MIL-STD-

1246B (Sep 1987).3 Baran, S. D., MSX Logistics and Transportation Plan, JHU/APL Doc. No. 7334-

9195 (11 Feb 1994).4 McDevitt, J., MSX Emergency Action Plan for APL, JHU/APL Doc. No. 7334-

9188 (Feb 1994).5 McDevitt, J., MSX Ground Safety Plan for Operations at Goddard Space Flight

Center, JHU/APL Doc. No. 7334-9064 (Jun 1994).6 McDevitt, J., MSX Ground Safety Plan for Operations at Vandenberg Air Force

Base, JHU/APL Doc. No. 7334-9184 (Sep 1994).7 Schick, S. H., SPIRIT III Operational Review for Payload Processing Facility and

SLC-2W, USU/SDL Doc. No. 016, Rev. 1 (Jun 1994).8 Johnson, J. L., MSX Program Protection Plan (Jul 1993).9 Johnson, J. L., MSX Program Protection Plan for Vandenberg Air Force Base,

JHU/APL Doc. No. 7334-9235 (Jun 1994).10Goss, M. E., MSX Product Assurance Plan, JHU/APL Doc. No. SOR-1-

89036A (Jun 1991).11Nagrant, J., Integrated Test Specification for Space Payload Equipment, JHU/APL

SDO 2387-1 (Feb 1982).12Technical Services Department Hardware Configuration Management Manual,

JHU/APL Doc. No. TSD-STD-400.1, Rev. 2 (Sep 1993).13MSX Program Test Plan, JHU/APL Doc. No. 7334-9001 (Jun 1994).14Sadilek, A. C., MSX Spacecraft Optical Mapping Plan at VAFB, JHU/APL Doc.

No. 7334-9245A (Sep 1994).15Hartong, G. S., MSX—Evaluation of the Potential for RF Environmental

Exposure of the MSX Spacecraft at VAFB During Launch Preparations andProcessing, JHU/APL Doc. No. S2R-94-273 (Oct 1994).

16Utterback, H. K., MSX Software Master Test Plan, JHU/APL Doc. No. S1A-021-90 (26 Feb 1990).

17Fox, H., Test Interfaces and Requirements Document (TIRDOC), JHU/APLDoc. No. 7334-9040 (Jun 1994).

18Baran, S. D., MSX Launch Site VAFB Operations Plan, JHU/APL Doc. No.7334-9009 (12 Aug 1994).

19Kreitz, H. M., MSX Handling and Prelaunch Operations at the PPF and LaunchPad, JHU/APL Doc. No. 7334-9046, Tasks 1-4 (Oct 1995), Task 5 (Mar1995).

20Huebschman, R. K., MSX Mission Operations Simulation Test at the PPF, JHU/APL Doc. No. 7334-9304A (Nov 1995).

21Bell, G. A., Fill and Top-off of SPIRIT III Cryostat in the Astrotech Building,USU/SDL Doc. No. 014, Rev. 1 (13 Jul 1994).

ACKNOWLEDGMENT: We would like to express our appreciation to the MSXground operations team members for their help in the preparation of this article.The MSX mission is sponsored by the Ballistic Missile Defense Organization. Thiswork was supported under contract N00039-94-C-0001.

JAMES F. SMOLA received a B.S. in mechanical engineering from the IllinoisInstitute of Technology in 1951 and an M.S. in applied mathematics from TheJohns Hopkins University in 1969. Since joining APL in 1958, he has been amember of the Space Department, and over the years he has been involved inthe development of many NASA and DoD spacecraft, with responsibilitiesranging from the design, analysis, and testing of structural systems to thedevelopment of attitude control and detection systems, aerospace mechanisms,and liquid, solid, and cold-gas propulsion. For the past 10 years, he has beeninvolved in the technical management of DoD programs at APL for SDIO andBMDO. Mr. Smola currently is the MSX Spacecraft Manager, the AssistantGroup Supervisor of the Space Department’s Guidance and Control Group, anda member of the Principal Professional Staff. His e-mail address [email protected].

THE AUTHORS

HNS HOPKINS APL TECHNICAL DIGEST, VOLUME 17, NUMBER 2 (1996)


CHRISTOPHER C. DeBOY received his B.S. in 1990 from the VirginiaPolytechnic Institute and State University (Virginia Tech) and his M.S. in 1993from The Johns Hopkins University, both in electrical engineering. In 1990, hejoined the RF and Microwave Systems Group of APL’s Space Department. Hiswork to date has focused primarily on the design and development of microwavecommunications and radar systems and their ground support equipment. Inaddition to being the lead MSX Ground Operations Communications Engineer,Mr. DeBoy is the field engineer for the MSX S-band and X-band flightcommunications equipment. His e-mail address is [email protected].

JOAN H. CRANMER received her B.S. degree from the Pennsylvania StateUniversity and her S.M. in materials science and engineering from theMassachusetts Institute of Technology. Before coming to APL, she worked atCOMSAT Laboratories in Clarksburg, Maryland, and at Rockwell International/North American Aviation in Los Angeles. She joined APL in 1987 and iscurrently a senior engineer in the Materials Laboratory in the Technical ServicesDepartment. In addition to work in spacecraft contamination control andmaterials selection, she is working in nonmetallic materials characterization andprocessing, primarily composites. Ms. Cranmer is the MSX ContaminationControl Engineer. Her e-mail address is [email protected].

MICHAEL H. BARBAGALLO is a Senior Professional Staff member of theAPL Space Department’s Systems Integration and Test Group. Since joiningAPL in 1972, he has been engaged in the integration and testing of DoD andNASA scientific spacecraft. Over the years he has worked as the payloadengineer on many space programs at APL, including the M131 rotating litterchair for the NASA Apollo Skylab and the NASA Apollo 17 Moon mission, theTransit Improvement Program, the Apollo Soyuz Test Project UltravioletAbsorption Experiment MA-059, the SATRACK missile translator, the GeosatA spacecraft, and the Delta 181 spacecraft. Mr. Barbagallo is currently the MSXSpacecraft System Engineer and Integration and Test Manager. His e-mailaddress is [email protected].

MARK J. HAROLD is a Senior Professional Staff member of the APL SpaceDepartment’s Mechanical Engineering Group. He received a B.S. in civilengineering from the Pennsylvania State University in 1979 and an M.B.A. fromthe University of Baltimore in 1991. Before joining APL in 1989, he was amechanical design engineer at the Boeing Military Aircraft Corp., working onthe 757, 767, and B52 aircraft; the Grumman Flxible Corp., working on the 870mass transit bus; and Martin Marietta Aero and Naval Systems, working on theU.S. Navy’s Vertical Launching Systems and Wide Aperture Array programs. AtAPL, he has been involved in the MSX mechanical design and the preparationof numerous spacecraft proposals. Mr. Harold is currently the MSX AssistantPayload Mechanical Engineer and is assisting in the design of the ACEspacecraft. His e-mail address is [email protected].

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J. F. SMOLA ET AL.

JULIE A. KREIN received her B.S. in mechanical engineering from theUniversity of Delaware in 1989. She began her career with General Electric’sAstro-Space Division in Princeton, New Jersey, where she was a member of theThermal Engineering Group. She worked on programs such as EOS and DMSP.She is currently an employee of Swales and Associates in Beltsville, Maryland,and has been working on-site at APL since 1993. While at APL, Ms. Krein hasbeen involved in the thermal design, analysis, and testing of MSX, and she willbe supporting the MSX launch. Her e-mail address is [email protected].

HARRY M. KREITZ, Jr., is a Senior Professional Staff member of the APL SpaceDepartment’s Mechanical Engineering Group. In 1966, he received a B.S. inmechanical engineering from the University of Maryland. Since joining APL in1991, he has been the MSX Payload Mechanical Engineer. In addition to MSX,Mr. Kreitz is assigned to the Active Geophysical Rocket Experiment as thePayload Mechanical Engineer. His e-mail address is [email protected].

ALBERT C. SADILEK received a B.S. in mechanical engineering in 1973 andan M.S. in applied mathematics in 1976 from The Johns Hopkins University.Mr. Sadilek joined APL in 1972 and was assigned to the Space Department’sGuidance and Control Group. His experience includes the design, assembly,testing, and on-orbit operation of a variety of spacecraft mechanisms, propulsionsystems, and mechanical subsystems. In addition, he was engaged in the design,testing, implantation, and clinical trials of biomedical devices, such as theProgrammable, Implantable Medication System and the Automatic ImplantableDefibrillator. He was also responsible for the MSX instrument purge system andoptical alignments of the spacecraft instruments and attitude sensors. Mr. Sadilekis a member of APL’s Senior Professional Staff. His e-mail address [email protected].

HARRY K. UTTERBACK received an A.B. in mathematics from GettysburgCollege in 1957 and an M.S. in computer science from The Johns HopkinsUniversity in 1975. He is a member of APL’s Principal Professional Staff assignedto the Space Department’s Computer Science and Technology Group. He alsoteaches in the G.W.C. Whiting School of Engineering Part-Time Programs inEngineering and Applied Science. Mr. Utterback has developed real-timesoftware systems for various spacecraft and ground systems since joining APL in1969. He has served as the chairman of the Independent Research andDevelopment Committee on Software Engineering. He is an emeritus member ofthe American Institute of Aeronautics and Astronautics Technical Committeeon Software Systems and a member of the Institute of Electrical and ElectronicsEngineers Computer Society. His current interests focus on managing andimproving the software development process. His e-mail address [email protected].

188 JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 17, NUMBER 2 (1996)

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