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Design Verification of MSL Second Chance. What is MSL Second Chance? Some Design Details Verifying the Design Summary Questions. Pradip Maitra TASC [email protected] What is Second Chance (SECC)?.

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Design verification of msl second chance

Design Verification ofMSL Second Chance

What is MSL Second Chance?

Some Design Details

Verifying the Design

Summary

Questions

Pradip Maitra

TASC

[email protected]


What is second chance secc
What is Second Chance (SECC)?

  • MSL has 2 Flight Computers (FC-A and FC-B) normally loaded with the same flight software (FSW) image.

  • Only FC-A is ON during Cruise and Surface Ops.

  • During EDL, the FC-B is also turned ON.

  • FC-B executes a different FSW image during EDL.

  • This FC-B image monitors FC-A state and actions.

  • If FC-A misbehaves, FC-B takes over control and resumes EDL operation within 1-2 seconds.

  • This was the intent of MSL Second Chance (SECC).


Design details
Design Details

  • 134 Second Chance requirements in addition to original 4446 FSW requirements.

  • Principal guidelines:

    • Do not harm existing FSW functionality as it is going to get changed to accommodate Second Chance.

    • SC Image will not share normal FSW image banks.

    • SC Functionality can be deactivated in the last moment.

    • SC Image will be uploaded 2 weeks before EDL.

    • SC Image will be forgotten immediately after landing.



Verifying the design
Verifying the Design

  • Reset Scenario Analysis.

  • Does any SECC requirement violate EDL Timeline?

  • How capable is SECC image in resuming EDL?

  • How SECC image interfaces with FSW environment?

    • SECC image upload and booting into it.

    • Unintended Enabling/Disabling/Arming SECC image.

    • Verifying receipt of “Prime in distress” event.

    • Where SECC image is being stored and can it affect normal FSW boot sequence?

    • Verifying successful removal of SECC image after landing.



Summary
Summary

  • The design verification work had uncovered a few problem areas that were judged to be of very low probability of occurrence.

  • JPL conducted a high resolution simulation of FC-A failures during different time points of EDL. Their simulation also found that not all possible failure periods can be covered using a 1.5 to 2 seconds recovery time.


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