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InSight Cruise Phase, Events during Mars transit prior to EDL
nprev
post May 8 2018, 05:35 AM
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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).


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Tycho
post May 10 2018, 08:27 PM
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Just to put it in my calendar: Is it possible to already determine at what time exactly the landing will happen? Does anybody know?
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Phil Stooke
post May 10 2018, 08:41 PM
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hasty reply deleted!

Phil


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mcaplinger
post May 10 2018, 09:25 PM
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Press kit says Nov. 26, 2018, about noon PST (3 p.m. EST; 20:00 UTC).


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Disclaimer: This post is based on public information only. Any opinions are my own.
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nprev
post May 11 2018, 12:01 AM
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Just out of curiosity <rimshot>, how much control over the landing date & time does InSight really have? Since it's a direct EDL I can't see the possible variance being more than a few minutes at most else it would miss the target area completely. Also, I'm sure that the amount of attitude control propellant on board is just enough to get that specific job done throughout cruise and entry with perhaps a small contingency reserve for leaks, etc.


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djellison
post May 11 2018, 12:25 AM
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The TCMs between now and entry are not only designed to reach the appropriate target - but to do so at the exact right time. If you're targetting the landing ellipse at the wrong time, they your entry angle will be bad. If you target the right entry angle, but at the wrong time...you won't be landing in your ellipse...and so on and so on.


Timing is also crucial so that MRO will be in the right place to record UHF telemetry during EDL (MRO can only store and forward that data - no realtime bent-pipe)

Hopefully, if they make it, the MarCOs WALL-E and Eva will conduct bent pipe realtime UHF to XBand!
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nprev
post May 11 2018, 03:49 AM
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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.





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Explorer1
post May 11 2018, 04:13 AM
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There is a bit of margin in terms of inclement weather though, right? If I recall, was it Spirit's landing that was modified a bit in the exact timing of certain sequences due to dust storms? Or was that Curiosity?
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djellison
post May 11 2018, 05:06 AM
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A shift in when to deploy the parachute.....but not a shift to the entry time and entry attitude. The landing time will remain unchanged to within a few seconds.

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djellison
post May 11 2018, 05:10 AM
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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.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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nprev
post May 11 2018, 07:14 PM
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Rocketcam video of launch and spacecraft separation:

https://spaceflightnow.com/2018/05/11/video...launch-to-mars/


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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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Explorer1
post May 11 2018, 08:02 PM
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QUOTE (nprev @ May 11 2018, 02:14 PM) *
Rocketcam video of launch and spacecraft separation:

https://spaceflightnow.com/2018/05/11/video...launch-to-mars/

Farewell InSight! Safe travels!

And not to be seen again by human eyes until the first good HiRise pass in November...
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Decepticon
post May 14 2018, 04:17 AM
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QUOTE (nprev @ May 11 2018, 02:14 PM) *
Rocketcam video of launch and spacecraft separation:

https://spaceflightnow.com/2018/05/11/video...launch-to-mars/



Was this shown Live?

I don't remember seeing this!?
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Explorer1
post May 14 2018, 02:09 PM
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No, it was released a few days later.
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Explorer1
post May 16 2018, 05:01 AM
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First light from the cubesats: https://www.jpl.nasa.gov/news/news.php?rele...ml&rst=7124

If all goes well in November, we might very well get a pale red dot too... getting larger and larger...
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