QUOTE (nprev @ May 10 2018, 08:49 PM)
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.pdfThe 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"