spacecraft bus specifications

Template: ASPERA-DOC-00001_Rev_1

Spacecraft Bus Specifications

Prepared by Kerry Gonzales

ASPERA-DOC-00002 Rev 2 July 13, 2021

RFP S182201 Attachment A

Spacecraft Bus Specifications ASPERA-DOC-00002 Rev 2 July 13, 2021

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SIGNATURES Approvers Approvers

K. Gonzales

Mission Systems Engineer - Author

N/A

T. McMahon

Mission Project Manager

N/A

Dr. C. Vargas

Principal Investigator

N/A

Dr. H. Chung

Co-Investigator

N/A

Dr. E. Hamden

Co-Investigator

N/A

N/A N/A


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REVISION LOG Version Date

mm/dd/yyyy Affected Section(s)

Engineering Change #

Reason/Initiation/Remarks

1 07/08/2021 All None Initial Draft

2 7/9/21 All None Draft 2

3 7/13/21 All None Initial Release


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TABLE OF CONTENTS 1 SCOPE ................................................................................................................ 7 1.1 Purpose ............................................................................................................. 7 1.2 Applicability ....................................................................................................... 7 2 APPLICABLE DOCUMENTS ................................................................................... 8 3 DEFINITIONS ...................................................................................................... 9 4 Mission Description ......................................................................................... 10 5 Scope .............................................................................................................. 11 5.1 Schedule .......................................................................................................... 11 5.2 Deliverables ..................................................................................................... 11 5.3 Options ........................................................................................................... 12 5.3.1 Virtual Software Package ............................................................................... 12 5.3.2 Extended Storage of Integrated Spacecraft .................................................... 12 5.3.3 Larger Propulsion Capability ......................................................................... 13 5.4 Bidders Instructions ......................................................................................... 13 6 Spacecraft Requirements .................................................................................. 14 6.1 Interfaces ........................................................................................................ 14 6.1.1 Launch Vehicle ............................................................................................. 14 6.1.2 Mechanical ................................................................................................... 14 6.1.3 Electrical ....................................................................................................... 14 6.1.4 Data ............................................................................................................. 15 6.2 Performance .................................................................................................... 15 6.2.1 Thermal ........................................................................................................ 15 6.2.2 Pointing ........................................................................................................ 15 6.2.3 Payload Safety .............................................................................................. 15 6.3 Engineering Support ........................................................................................ 16 6.3.1 Systems Engineering ..................................................................................... 16 6.3.2 Mechanical/Thermal Engineering Analysis .................................................... 16 6.4 Integration and Testing .................................................................................... 16 6.5 Mission Compatibility ...................................................................................... 17 6.6 Launch and Operations .................................................................................... 17 6.7 Project Communication .................................................................................... 18 7 REFERENCES ..................................................................................................... 19 9 Appendix A ...................................................................................................... 20


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FORWARD This document is an Aspera Project controlled document. Changes to this document require prior approval of the Aspera project Configuration Management Team. Proposed changes shall be submitted to the Aspera Change Control Board along with supportive material justifying the proposed change. Changes to this document will be made by complete revision. Questions or comments concerning this document should be addressed to: Aspera Configuration Management Team.


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ABBREVIATIONS AND ACRONYMS Table 1: Abbreviations and Acronyms

Phrase/Acronym Description

CDR Critical Design Review

ConOps Concept of Operations

Dec Declination

EMC Electo-Magnetic Contamination

EOC Execution of Contract

NASA National Aeronautics and Space Administration

OVI Oxygen VI

PC Personal Computer

PDR Preliminary Design Review

POC Point of Contact

RA or R.A. Right Ascension

SSO Sun Synchronous Orbit

TBC To Be Confirmed

TBD To Be Determined/Defined

TRL Technical Readiness Level

TVAC Thermal Vacuum

UArizona University of Arizona

UV Ultraviolet


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1 SCOPE

1.1 Purpose

This document details the specifications for a spacecraft bus that is required to complete the Aspera mission. The spacecraft bus is intended to interface with the Aspera payload (UArizona delivered) to complete the mission flight hardware.

1.2 Applicability

All specifications herein apply directly to the deliverable spacecraft bus and all interactions with the Aspera payload hardware, software, and project team.


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2 APPLICABLE DOCUMENTS The following documents of the exact issue shown form a part of this specification to the extent specified herein. In the event of conflict between the documents referenced herein and the contents of this specification, the contents of this specification shall be considered a superseding requirement.

Table 2: Applicable Documents

Ref. Document # Title

AD-1

AD-2

AD-3

AD-4

AD-5

AD-6

AD-7

AD-8

AD-9

AD-10

AD-11

AD-12

AD-13

AD-14

AD-15

AD-16


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3 DEFINITIONS The following definitions apply to terms used in this manual:

Table 3: Definitions

Term Definition

Anti-Sun The vector direction 180 deg from the Sun

Boresight The vector direction of the primary optical axis of the telescope


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4 Mission Description The University of Arizona (UArizona) team, led by Principal Investigator Dr. Carlos Vargas, is developing a small satellite science mission named Aspera which has a planned launch date in early 2025 (TBD). The Aspera mission goals are to detect and map OVI emissions in galaxies near the Milky Way. A four-channel telescope-spectrograph with micro channel plate detectors operating in the ultraviolet comprises the science instrument. Other payload elements include high and low voltage power supplies, computer and data handling devices, survival heating elements, and various sensors needed to operate the spectrograph. The mission will launch as a PIONEERS program on a rideshare provided by NASA. The details of the launch vehicle will not be known until later in the project cycle. Therefore, certain assumptions pertaining to spacecraft weight, dimensions, and launch vehicle interfaces are made in this document to allow for versatility in launch partner. The intended mission orbit is a low-earth, dawn-dusk Sun synchronous terminator orbit (SSO) at a preferred altitude of 700-900 km. The instrument boresight will nominally point anti-sunward. Mission objectives are to observe 10 nearby galaxies over a mission lifetime of 10 months. This timeframe includes a 1-month (anticipated) start-up and commissioning phase immediately after orbit is achieved followed by the science data collection phase. The mission target list and discussion of “a day in the life” of the Aspera mission are included in Appendix A. Calibration targets will also be selected periodically (TBD) to ensure the instrument is operating correctly and data can be verified. The concept of operations (ConOps) includes at least one data downlink per day with an uplink of any housekeeping tasks and mission planning commands. At the completion of the mission the Aspera spacecraft must successfully deorbit as prescribed by the NASA guidelines for small-sat missions. An important part of mission success is selection of a spacecraft bus that meets the mission requirements which are detailed in the following sections.


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5 Scope The University of Arizona team is seeking a spacecraft vendor to be an integral part of the Aspera mission. The successful bidder will have a desire to work closely with the UArizona team to develop a synergistic integrated spacecraft within the guidelines provided by the NASA PIONEERS program.

5.1 Schedule

The PIONEERS program has a fairly short lifetime that covers design, fabrication, testing, and delivery of the fully integrated spacecraft, followed by a 10 month on-orbit lifetime. Due to the nature of ridesharing, there could be a waiting period between spacecraft completion and launch. The expected project schedule is outlined in Table 4 below.

Table 4: Aspera Nominal Schedule

Aspera Milestones Nominal Date Project Aspera Start 4/1/21 Concept Design Report 8/31/21 System Requirement Review (SRR) 10/13/21 Execution of Contract (EOC) w/ Spacecraft vendor EOC Spacecraft Preliminary Design Review (SC-PDR) EOC+6mo Spacecraft Critical Design Review (SC-CDR) EOC+14mo Spacecraft bus ready EOC+22mo Payload Flt. Unit Delivery EOC+25mo PL Integration with SC complete EOC+27mo Environmental Testing complete EOC+31mo Launch readiness review EOC+32mo Launch (Nominal) EOC+34mo Commissioning complete Launch+1mo End of Science Ops support Launch+10mo End of Mission support Launch+11mo

5.2 Deliverables

The spacecraft vendor will be responsible for the following deliverables: ● One flight unit spacecraft bus (fully integrated, see Section 6)


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● A “flat sat” for bench testing (or loan, or remote access to for integration with continued access as necessary for debugging during on-orbit operations)

● Participation in project related reviews at UArizona and NASA facilities and/or online equivalent

● All related project documentation, including but not limited to o Design documentation and drawings o Complete Bill of Materials o Review presentation materials o Clean assembly plan / contamination control plan o Test plan o Launch campaign plan o Operations plan and training material o Software user manuals o Component heritage and TRL classifications as needed

● Engineering support for commissioning ● Ground segment contracting and support ● Ground segment software and coordination ● Perform environmental (EMC, vibration, thermal vacuum) testing of

the integrated spacecraft/payload system. ● Data archiving coordination with UArizona chosen archiving

platform ● Training of UArizona personnel in spacecraft operations and

troubleshooting ● Launch and early operations commissioning of the spacecraft bus.

5.3 Options

The follow list are options that UArizona is interested in the spacecraft provider providing to the project:

5.3.1 Virtual Software Package

A virtual software simulator “soft sim”. The “soft sim” is a version of the spacecraft flight software and science flight software that run on a PC or simple computer used for simple debugging and verification.

5.3.2 Extended Storage of Integrated Spacecraft


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Clean and safe storage of the fully integrated spacecraft, for up to 2 years, at the vendor’s facility or other location subject to project approval. Storage must include the availability of continuous GN2 purge if needed by the payload.

5.3.3 Larger Propulsion Capability

The design and implementation of a propulsion solution that can achieve 200 m/s in Delta V.

5.4 Bidders Instructions

The bidder shall: - Provide a cost breakdown of the Deliverables - Provide a cost breakdown of the Options - Provide a narrative of their flight hardware heritage for missions

similar to Aspera. This narrative must include descriptions of hardware that has not yet reached a minimum of TRL 6 according to the NASA guidelines and describe a path for such qualification prior to the project Preliminary Design Review (PDR).

- Details on their ability to meet the aggressive project schedule considering any other commitments or anticipated delays.

- Propose a schedule and milestone payments that support the schedule above for consideration by the UArizona team. Include brief description of the spacecraft schedule critical path.

- Provide details on any exceptions taken to the requirements stated in this document and/or associated request for proposal documentation.

- Provide a description of any Warranty Terms and Service Maintenance Costs.

- Indicate if shipping/packaging is included in the cost breakdown. - Provide a description of the facilities and testing equipment to be

used in the spacecraft build and testing.


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6 Spacecraft Requirements

6.1 Interfaces

6.1.1 Launch Vehicle

The spacecraft bus shall interface to the launch vehicle using a 15” ESPA ring separation system. A common system is the RUAG PAS 381S (15”) as listed in the 2020 SMD ESPA RUG – Pioneers from NASA.

6.1.2 Mechanical

The fully integrated spacecraft shall fit within the ESPA payload volume interface requirement (2020 SMD ESPA RUG – Pioneers Table 6.1) of 24” x 28” x 38” in Y, Z, X dimensions where X is defined as the direction normal to and beginning at the ESPA port interface plane. The current best estimate of payload volume is 360mm x 360mm x 560mm. The fully integrated spacecraft shall not exceed the ESPA payload mass interface requirement (2020 SMD ESPA RUG – Pioneers Table 6.1) of 220 kg in total mass. The current best estimate of payload mass is 24 kg (not including margin). The fully integrated spacecraft shall have a lowest resonant frequency greater than 75Hz. The spacecraft vendor shall coordinate with UArizona engineers to determine payload effects on this requirement. The fully integrated spacecraft shall have a peak line load across the ESPA ring interface of no more than 400 lb/in (see 2020 SMD ESPA RUG – Pioneers Section 6.3.4). The spacecraft bus structure shall fully envelop the payload providing protection for all payload components.

6.1.3 Electrical

The spacecraft bus shall supply a minimum of 12V +/- 1V unregulated power to the payload. The payload power requirements are 27W/43W nominal/peak (without margin). The Sun synchronous orbit will have periodic eclipses (up to 20 min duration expected) and power delivery to the payload during these events must be considered when sizing


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the power system to accommodate survival heaters within the payload.

6.1.4 Data

The spacecraft shall supply an appropriate ground communication system that can achieve at least one downlink per day at 1.6 Mbps for a total expected daily volume of 0.14 GB. The spacecraft shall be capable of storing at least 4 GB of data.

6.2 Performance

6.2.1 Thermal

The spacecraft shall provide a payload operational temperature of 293K +/- 20K. The payload survival temperature range is 243K – 313K.

6.2.2 Pointing

The spacecraft shall have a pointing accuracy of 7.2 (1σ) arcsec or better. The spacecraft shall have a pointing knowledge of 5.5 (1σ) arcsec or better. The spacecraft shall have a pointing stability of 1 arcsec/sec or better. The roll control of the spacecraft shall be better than 3 arcmin. The spacecraft shall allow for off anti-sun pointing of the payload boresight up to 40 deg to maintain a continuous power-positive state. The spacecraft shall provide a maximum slew rate of 5 deg/min. The spacecraft bus is expected to include 2 or more star trackers to meet all pointing requirements (see discussion in Appendix A).

6.2.3 Payload Safety

The spacecraft shall detect solar incidence within 45 deg of the Sun and automatically deploy a safety system to protect the telescope


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from accidental solar exposure. The spacecraft shall also automatically recover operational status after the safety system has deployed. The spacecraft vendor shall design and implement active aperture covers for the telescope optical boresight. These covers shall be capable of multiple open/closing cycles and shall comprise a part of the Sun avoidance safety system on the spacecraft.

6.3 Engineering Support

6.3.1 Systems Engineering

The spacecraft vendor shall provide systems engineering support to assist with mission requirements analysis, documentation management and configuration control, 3D model control, and provide project level participation at all project peer reviews and high-level program reviews with NASA.

6.3.2 Mechanical/Thermal Engineering Analysis

The spacecraft vendor shall provide mechanical/thermal engineering support for and design the combined spacecraft and payload thermal control system ensuring the operational requirements are met. The spacecraft vendor shall implement and test the thermal system design in a thermal vacuum test chamber (TVAC).

6.4 Integration and Testing

The spacecraft vendor shall provide facilities for and execute the integration of the payload and spacecraft bus. The spacecraft vendor shall provide facilities to conduct environmental testing, including but not limited to EMC, vibration, and TVAC. The spacecraft vendors’ integration facility must meet or exceed the class 10,000 clean room specification (ISO 7). Class 1000 flow benches are also desired for integration activities. A detailed clean assembly plan or contamination control plan will be required to ensure payload cleanliness during integration and testing activities. The Aspera mission, operating in the UV, contains specially coated optical


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elements that are highly sensitive to molecular contaminates which require extremely low humidity environments that also meet the ISO 7 clean specification. The spacecraft vendor shall permit up to 4 UArizona project personnel to participate in and witness all integration and testing activities as needed. At least two weeks’ notice on the confirmed schedule is required to allow for planning UArizona travel to the vendor facility. The spacecraft vendor shall deliver a software simulator “soft sim” for use by the payload engineering team for testing of the flight software integration. The delivery date of this “soft sim” shall be determined and agreed during the initial design phase of the project. The spacecraft vendor shall provide and/or provide access to a “flat sat” hardware/software set for bench testing of the full system. A shipping and storage plan shall be developed to ensure the payload cleanliness in the event any part of the spacecraft must be stored for any period of time and include details for the final delivery of the fully integrated spacecraft to the launch provider to ensure payload cleanliness.

6.5 Mission Compatibility

The spacecraft shall use only high vacuum compatible, low-outgassing (NASA Reference Publication 1124) materials, adhesives, and lubricants. A detailed bill of materials must be provided. Proposed bake-out of outgassing components is allowed, subject to project approval. The spacecraft shall include an inert propellant propulsion system capable of 100 m/s Delta V for initial orbit placement, station keeping, and deorbit maneuvers as needed.

6.6 Launch and Operations

The spacecraft vendor shall execute the initial start-up and commissioning of the spacecraft in orbit. UArizona personnel will assist in the commissioning phase. The spacecraft vendor shall provide training in spacecraft operations to UArizona personnel during the commissioning phase.


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The spacecraft vendor shall provide on-call support for the operation of the spacecraft over its entire 10-month lifetime. The spacecraft vendor shall propose, coordinate, and execute an agreement for the Ground Segment of the project. The UArizona team will coordinate with the spacecraft vendor to arrange licensing.

6.7 Project Communication

Spacecraft bus engineering representative(s) shall be present at any project level review with UArizona and/or NASA as needed to address the spacecraft interface. The spacecraft vendor shall appoint a designated point of contact person for all technical interactions. A contractual POC can be separate from the technical POC. The spacecraft vendor shall deliver all technical documentation and user manuals on the agreed schedule dates. These documents shall include: design documentation and drawings, review presentation materials, clean assembly plan / contamination control plan, spacecraft test plan, launch campaign plan, operations plan and training material, software user manuals, component heritage and TRL classifications as needed, and any other pertinent documentation developed as a part of the project. The spacecraft vendor shall implement a configuration management process and comply with all UArizona configuration management policies and procedures.


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7 REFERENCES Table 5: References

Ref.

Document/Location Description

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[14]

[15]

[16]

8


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9 Appendix A


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