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In the recently proposed entry of Red Dragon into the Mars atmosphere, the supersonic retro-propulsion (or SRP, roughly: slowing down using thrusters while still moving against the atmosphere at supersonic speed) data collection will be extremely valuable.

But this comment got me thinking...

I am sure a huge amount of data will be collected and stored - to be broadcast later when things have settled down simply due to the volume of data collected vs bandwidth.

If for some strange reason there is an unanticipated catastrophic event, will there be at least some real-time radio broadcast of telemetry (to anywhere - Mars satellite, earth, etc.) during the SRP? If not, is it because there is a (radio) Communications Blackout due to heating and ionization or other similar phenomenon?

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uhoh
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Not much is known about Red Dragon yet. There will be a brief communications blackout. For Mars the blackout period is around 30 seconds.

Detailed study of comms blackout for Mars. Blackout is related to electron density, which depends on the speed/altitude profile.

This article discusses the analysis of the UHF communications blackout (and brownout) experienced by the Mars Science Laboratory (MSL) during the period around peak heating of its entry, descent, and landing (EDL) phase into the Martian atmosphere on August 6, 2012. The UHF relay links from MSL to the Mars Reconnaissance Orbiter (MRO) and to the Mars Express (MEX) suffered a period of ~70 s of degradation, consisting of a combination of brownout (signal fades) and blackout (complete loss of signal) that coin- cided with the predicted period of signal degradation from preflight analyses.
Earlier work involving an analysis of entry vehicles into the Martian atmosphere included a postflight study of the 30-s signal outage suffered by the Mars Pathfinder spacecraft in 1997 at X-band on a direct-to-Earth (DTE) link, attributed mostly to charged particles 2.

Hobbes
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  • Thanks! Can you help me find a link-able source for the 30 seconds estimate? Might it be longer for something with substantially more kinetic energy to dissipate? I'm guessing Dragon will have a lot more mass than Curiosity. – uhoh May 01 '16 at 10:53
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    30 seconds was for Pathfinder, MSL had a longer blackout. – Hobbes May 01 '16 at 11:10
  • Wow - that paper is excellent! It's full of data and systematic discussion and analysis. Thank you @Hobbes! – uhoh May 01 '16 at 11:19