InSight Cruise Phase, Events during Mars transit prior to EDL |
InSight Cruise Phase, Events during Mars transit prior to EDL |
May 8 2018, 05:35 AM
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Hey again, everyone. This thread will be for discussion of anything that happens between now & landing day, currently 26 Nov US Pacific time (UTC-8 hrs during that part of the year).
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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May 11 2018, 03:49 AM
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Got it, and thanks for the great details, Doug. So, there is very little flex possible (none, really; it's all about error correction).
X-band...yes, please, and here's rooting for the MarCOs! A bit surprised that MRO doesn't have a bent pipe capability while MODY does, but I assume that's probably because a- MRO's primary mission payloads took up the mass budget and b- nobody seriously thought at the time that we'd have more than one operational surface asset AT a time for long enough to justify it. -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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May 11 2018, 05:10 AM
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
A bit surprised that MRO doesn't have a bent pipe capability while MODY does, So - as I understand it - MRO could, kind of, do a semi immediate store and forward approximating a bent pipe. It's not a mass problem. (TGO and MAVEN have basically the same UHF antenna and Electra radio system). BUT - the choice has been made to record data in an open loop canister mode. Not immediately decoding the 1's and 0's - but recording all the Electra can hear. This entire data set will then be dumped back to Earth enabling a deeper analytical dive into the data if something goes wrong, and to throw computationally intensive analysis at it that MRO couldn't do in real time. Back when MSL landed - MRO was doing the same thing, but Odyssey was also overhead doing the bent pipe. If you could only have one - you would take the recorded data because while it lacks immediacy of bent pipe....it makes up for it in potential to have more useful information after the fact. The relevant facts start on page 28 - https://descanso.jpl.nasa.gov/DPSummary/MRO_092106.pdf The MRO - MSL Mode is discussed on page 108 - https://descanso.jpl.nasa.gov/DPSummary/Des...MSL_Telecom.pdf "MRO cannot provide delay-free (bent-pipe) relay, as it first records the return-link relay data as it is received from the descending spacecraft during the overflight and then sends the data to the DSN. Both telemetry relay (specifically, unreliable bit-stream reception at MRO for EDL and the Proximity 1 protocol [6F26] for normal relay) and open-loop recording (known as canister mode in CE505 radio terminology) are being considered for the relay reception onboard MRO. The current baseline is open-loop recording on MRO during EDL. However, open-loop recording was successful during Phoenix EDL. MSL will choose either Prox-1 unreliable or open loop for EDL in 2012 based on the predicted link signal level and variability. " This... https://ipnpr.jpl.nasa.gov/progress_report/42-197/197A.pdf appears to discuss it after the fact on page 6 "The UHF signal emitted by MSL was received by MRO’s Electra radio. The in-phase and quadrature components of the signal were recorded on board MRO in open-loop fashion. These signal data were relayed to a NASA DSN antenna on Earth over MRO’s DTE X-band telemetry link. The spectra extracted from the open-loop data as a function of time were examined and processed at different bandwidths to extract carrier-to-noise ratio (CNR) and frequency estimates" |
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