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InSight Cruise Phase, Events during Mars transit prior to EDL
Guest_mcmcmc_*
post Nov 24 2018, 03:53 PM
Post #101





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QUOTE (mcaplinger @ Nov 24 2018, 04:34 PM) *
You need to calm down a little.

Certainly for previous landings there have been a lot of simulations of what the attitude on chute was, and we used them to calculate exposure times, photometric angles, etc, but at best they were measures of what could have happened. Nobody expected them to look much like reality, and they didn't. For example, the MSL descent was much less oscillatory than some of the simulations.

I have 4 questions about parachute-to-landing phase:
1) which is the maximum tilt any lander can tolerate for a safe landing?
2) which is the maximum transverse wind speed any lander can tolerate for a safe landing?
3) How can I determine the better direction for BAM if I don't know wind direction and speed?
4) How can we answer above questions without any method available to know lander tilt and wind speed and direction during landing? (or maybe there are methods, but I dind't find them in stuff I 've read).


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mcaplinger
post Nov 24 2018, 04:25 PM
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The way EDL is validated is that many Monte Carlo runs are done with all of the parameters varied across their expected ranges and we see if the landing is successful.

Most of this is covered by ITAR so I wouldn't expect to see public information about the specifics.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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mcaplinger
post Nov 24 2018, 04:41 PM
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QUOTE (mcmcmc @ Nov 24 2018, 07:53 AM) *
How can we answer above questions without any method available to know lander tilt and wind speed and direction during landing?

The tilt at landing is well-known from looking at the gravity vector and the vehicle is actively controlling its attitude during powered descent. The tilt in the last 10 seconds of parachute descent, for example, is completely irrelevant to the tilt at landing.

Varying atmospheric conditions are the major reason that the landing ellipses are relatively large.


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Guest_mcmcmc_*
post Nov 24 2018, 05:43 PM
Post #104





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To "touch with your hand" Insight, or at least to get an idea of its real size, here it is the official NASA JPL app with ARCore support (i.e. no printed markers needed, just Android 7+ and a floor):
https://play.google.com/store/apps/details?...aftAR&hl=en

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Guest_mcmcmc_*
post Nov 24 2018, 07:14 PM
Post #105





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QUOTE (nogal @ Nov 24 2018, 03:23 AM) *
Here it is, quick and dirty, using Phoenix's EDL data (rotated and re-centered). You have to play with the slider controls to see the full path. Maybe I'll polish it latter but right now it is way past my shuteye time. Cheers

Fernando

[attachment=43737:InSight_EDL_Sim.kmz]

This file includes:
- same descent profile of my previous file (centered on Phoenix landing site)
- different images with transparency, representing lander in various configurations.

Unfortunately I can no more work on it till 2018-11-25 10:00 GMT, maybe you've best luck?
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nogal
post Nov 24 2018, 11:37 PM
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[Unfortunately I can no more work on it till 2018-11-25 10:00 GMT, maybe you've best luck?
[/quote]
Thank you so much for sharing. I'm afraid I won't be able to work on them until mid week...
Cheers

Fernando
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nprev
post Nov 25 2018, 01:02 AM
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Here's a useful timeline of EDL and post-landing events. If all goes well we may see a surface image as early as 1204 PDT (2004 GMT); however, this may not happen until the following day.

I don't know what the landing site local time will be.


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dmuller
post Nov 25 2018, 03:56 AM
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QUOTE (mcmcmc @ Nov 24 2018, 11:34 PM) *
Declared sources for Horizons data:

CODE
Trajectory files                           Start (TDB)           End (TDB)
  --------------------------------------  -----------------   -----------------
  od002_v1.V0.1                           2018-May-05 12:39   2018-May-05 21:00
  od037_v1_delTCAL.V0.1                   2018-May-05 21:00   2018-Jun-08 00:00
  od092_v1.V0.1                           2018-Jun-08 00:00   2018-Jul-29 00:01
  od102_v1.V0.1                           2018-Jul-29 00:01   2018-Nov-25 19:40
  4day_landed.V0.1                        2018-Nov-25 19:40   2018-Nov-29 19:40


are we missing something?!?


They made a mistake, seem fixed now (at least the wrong day above)
CODE
od110_v2_V0.1                           2018-Oct-12 19:00   2018-Nov-26 19:40
4day_landed.V0.1                        2018-Nov-26 19:40   2018-Nov-29 19:40


It seems Horizons has flight data to entry interface, and from then on static, on the ground coordinates for 4 days. I.e. no EDL data in Horizons, which I dont think they ever had anyway. I suspect, however, they may have pasted the static data a tad too early over the flight data.
CODE
A.D. 2018-Nov-26 19:39:59.0000     3,543.74
A.D. 2018-Nov-26 19:40:00.0000     3,393.11 (distance from Mars center to landing site)

At :39:59 distance is about 20km greater than for nominal EI (125km above equator radius Mars, or 3522 from center), so that data infers EI at 19:40:16. I'll check back in 24 hours, will update my stuff then. The good thing is, Mars will be there, regardless :-)


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Phil Stooke
post Nov 25 2018, 04:34 AM
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https://mars.nasa.gov/insight/multimedia/raw-images/

This is where we will get to see the images as they come in.

Phil


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MahFL
post Nov 25 2018, 06:09 AM
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Is the last TCM going to be used ?
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nogal
post Nov 25 2018, 02:15 PM
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QUOTE (nprev @ Nov 25 2018, 01:02 AM) *
I don't know what the landing site local time will be.
The press kit says "mid afternoon on a winter day" (see page 13)
Fernando
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nprev
post Nov 25 2018, 06:10 PM
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Bit late, but press briefing live now. Appears that there will be a TCM-6 later today.

EDIT: Great brief. Lots of detail on MARCO and the seismometer thus far. The replay will be worth watching. Also just spotted Emily in the front row, and she's asking the first question! smile.gif

EDIT2: TCM-6 will be "a few cm/sec" delta V, will offset current target point approx. 11 nm (yeah, I know) SE to avoid rougher terrain.

EDIT3: Forgot to mention that Emily's questions involved MARCO. Periapsis around 2500-3000 nm, imagery will be attempted but not guaranteed due to tech demo nature of mission. Was emphasized that the cams were off-the-shelf.


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nogal
post Nov 25 2018, 09:40 PM
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Here is a new version of the EDL simulation. Just a few tweaks, really, all I had time to do, but it includes the original ellipse and the new one that was presented at today's briefing. I could be wrong because I had just a few seconds to see it and it seemed to me its center was ENE and 11 km from the old. nprev says 11nm SE.
Anyway, here it is.
Fernando
Attached File  InSight_EDL_Sim.kmz ( 17.32K ) Number of downloads: 269

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nprev
post Nov 25 2018, 10:25 PM
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<shrug> I could be wrong too about the direction. Think that what was said was that the terrain 11 (nautical?) miles (note the units!) NW of the original target point was potentially unsuitable so TCM-6 was gonna shift away from that.


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MahFL
post Nov 25 2018, 10:35 PM
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QUOTE (nprev @ Nov 25 2018, 10:25 PM) *
<shrug> I could be wrong too about the direction. Think that what was said was that the terrain 11 (nautical?) miles (note the units!) NW of the original target point was potentially unsuitable so TCM-6 was gonna shift away from that.


The landing point before TCM 6 was in less suitable terrain, so it's been moved 11 miles SW to a better place with TCM 6.

One question I never heard was how accurate is the desired landing point to where they actually land, usually ?
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