Onboard CORBA StudiesProject Review

Kevin Rice GST/NASA-GSFC Code 588

April 2001

Project Phases

• Phase 1– Port satellite flight software to CORBA

• Phase 2– Port “micro” CORBA to flight u-controllers– Connect u-controllers & main CPUs via PPP over

MUX-1553 bus, using CORBA• Phase 3

– Develop “ground to space” CORBA experiment in lab environment

– Possibly team with Science System Ltd (Plc) for flight experiments on UoSat-12

GSFC Flight Software Heritage

MAP 6/01?

XTE 12/95 TRMM 11/97 FUSE 6/99

SAMPEX 7/92 FAST 8/96 SWAS 12/98 TRACE 12/97WIRE 3/99

TRIANA ???

Architecture:!ANSI C!1 main flight computer! several u-controller sub-systems!1553/1773 ‘network’!VxWorks

Architecture:!C++!1 main flight computer!VxWorks

Use MAP Flight Software

• Microwave Anisotropy Probe• Follow on to COBE• Measures the cosmic micro-wave

background radiation in the Universe• Will launch in early summer 2001• Well understood by GSFC flight software

branch & largely finished…• Written in ANSI C

RT

R000

RT

R000

RT

R000Power RSN HouseKeeping

RSNTransponder

RSN(A)BC

Mongoose-V

MAC Processor

(A)

1773 Bus

MSSP

MAP Hardware Architecture Diagram (Simplified)

IRU

CSS

DSS

RWA

PCS

R000

RTRTACE

Custom I/O

ACERSN (A)

R000

RT

DEURSN

Sensors

•~12-14Mhz•32MB of “program memory”•256 MB recorder storage,•VxWorks

•Harvard Architecture•64K IRAM•64KDRAM•Custom RSN-OS•( 160k, 1MB of IRAM possible)1553/1773

MUX BusInterconnect

Basically a Distributed Architecture

Ground System

Phase 1: MAP Software Architecture Overview

1773

Medium Speed SerialLine

MAC Processor

Software Bus

Time Code Task

1773 Bus Controller Task

Checksum Task

Command Ingest Task

Mem. Scrub Task

Memory Dwell Task

Ephemeris Task

Attitude Control Task

Instrument Support Task

Data Storage Task

Telemetry Output Task

Telem. & Stat. TaskHealth &

Safety Task

Stored Command Task

CMD & Tel.

Transponder Power Attitude Control Housekeeping Digital Sensor Input

XRSN PSERSN ACE HK DEU

The SBUS is used as

the message passing

“channel”

MSG

MSG

MSG

Phase 1: CORBA PORT

1773

Medium Speed SerialLine

NT Processor

RT Events

Time Code Task

Checksum Task

Command Ingest Task Mem. Scrub

Task

Memory Dwell Task

Ephemeris Task

Attitude Control Task

Instrument Support Task

Data Storage Task

Telemetry Output Task

Telem. & Stat. TaskHealth &

Safety Task

Stored Command Task

CMD & Tel.

Replaced SBUS with TAO Real-time Event

Channel

1773 Bus Controller Task

Transponder Power Attitude Control Housekeeping Digital Sensor Input

XRSN PSERSN ACE HK DEU

Actually ported Linux PORT of

MAP to CORBA, on NT

CMD & Tel.

MSG

Ground System

MSG

MSG

Phase 2: Use Micro-CORBA ORB

• Science Systems Ltd (Plc) developed a small flight ORB for their RATE experiment

• RATE flew on the STRV-1b satellite last fall with goal of testing CORBA “calls” ground to space…

• Unfortunately, the STRV-1b failed shortly after launch…

• The RATE ORB can be configured to 5-20k depending on desired functionality.

• BUT it is NOT a full featured ORB, or necessarily 100% CORBA compliant…

Phase 2: Port Micro-CORBA to RSNs

• Science System agreed to provide binary version of CORBA using our cross-compilers

• Run PPP over 1553/1773 bus to provide “network” link…

• Map GIOP over PPP, or use GIOP+TCP+PPP if limited address space permits (easiest)

Phase 2: Micro-CORBA + GIOP + PPP

1773

Medium Speed SerialLine

MAC Processor

RT Events/RMI?

Time Code Task

1773 Bus Controller Task

Checksum Task

Command Ingest Task

Mem. Scrub Task

Memory Dwell Task

Ephemeris Task

Attitude Control Task

Instrument Support Task

Data Storage Task

Telemetry Output Task

Telem. & Stat. TaskHealth &

Safety Task

Stored Command Task

CMD & Tel.

Transponder Power Attitude Control Housekeeping Digital Sensor Input

XRSN PSERSN ACE HK DEU

PPP

Ground System

MSG

MSG

MSG

Use micro-ORB here, RTEMS, plus 1MB

of ram

Continue using

ACE/TAOhere

Use 50% of 1553 as serial stream for PPP

Phase 3: CORBA Ground to Space

• Develop in lab “flat sat” test bed to simulate ground to space CORBA

• Possibly experiment with simulated link delays and alternative protocol suites– TCP, SCPS-TP, CCSDS (using ORB level re-

transmission of GIOP?)• Team with Science Systems Ltd on RATE

“2”, using UoSAT-12

Phase 3: CORBA Ground to Space Concept

End-User ORBControl Center ORB(s)ORB Bridge?

Protocol Gateway?

Flight ORB

TCP/IPTCP/IP

GIOPGIOP

TCP or SCPS-TP

CORBA

TCP/IIOP

SCPS-TP?

GIOP

ORB Router?

Phase Status

• Phase 1:– Complete, but limited testing…

• Phase 2:– Currently working w/OAR Inc, to port RTEMS-OS to

u-controller, RTEMS can be configured to 32-120K with TCP stack (An RSN 160KB, or 1MB will need to be used…)

– July ’01 to start work w/SSL to port micro-ORB • Phase 3:

– SSL secured funding with BNSC for UoSat-12 experiments

– NASA-GSFC seeking funding…

Conclusion

• CORBA not quite ready for space environment, footprint is too large, performance is suspect…

• But functionally, it’s just what we need, and could be applied in a variety of ways from ground system design, to flight software, to more esoteric ideas like “CORBA ground to space…”