InSight mission Options

[SFJCody]

Following on from the earlier active seismic experiment suggestion, would the following idea have any merit whatsoever?


By the time InSight has landed on Mars the Falcon Heavy should have started operations. Falcon Heavy has a TMI capability of approx 17 tonnes
(mininum energy). Let's say that you want something better than minimum energy (as the aim is to maximize the velocity with which the impactor spacecraft intercepts Mars) and restrict the spacecraft to a mere 10 tonnes. Maybe a shorter direct flight would be best to set this up, maybe something more intricate involving multiple Venus & Earth 'gravity assists' would be preferable. Anyway, the capability exists, what about the spacecraft? I suppose it must be the opposite of most EDL designs. By this I mean that the aim is not to safely decelerate your vehicle but to smash into the ground with as much of the velocity you entered the atmosphere with as possible. Rather than a wide gumdrop shape you would want a sleek aerodynamic cylindrical shape like a rocket. You would want to enter the atmosphere perpendicular to the surface of the planet. You would favour high altitude regions over low altitude ones. Lastly, you would want a vehicle that is as dense as can be achieved. I suggest making the impactor out of depleted uranium because it's much cheaper than tungsten. So, a ten tonne metal cylinder hitting the surface of Mars at tens of km/s. Should make a nice bang!

For a twofer, the spacecraft could be targeted to mid-latitude areas suspected of having ice within metres of the surface and the resultant impact crater could be examined by HiRISE.

[nprev]

Couple things here to keep in mind:

1. F9 Heavy hasn't even flown yet.

2. F9 non-heavy hasn't been contracted to fly any NASA UMSF missions at all to date.

3. Anything intentionally landing or impacting on Mars has to comply with PPP (planetary protection protocols). Sterilizing an upper booster stage to this degree in probably not at all practical.

Not trying to rain on the parade, just think that we should confine this discussion to what InSight is really going to be capable of doing.

[SFJCody]

Not trying to rain on the parade, just think that we should confine this discussion to what InSight is really going to be capable of doing.

Of course. Just speculating a little. Wasn't trying to derail the main conversation.

[djellison]

We already know from the fresh craters found by CTX et.al. that we don't have to wait long for mother nature to do exactly that anyway.

[climber]

There is something confusing to me. On January 17th 2007 (as I've said in another topic) I ran into (MER and) MSL EDL team in LAX. I spoke with Miguel San Martin as follows:
- So, how everything’s going?
- Well, we’re working on the next one (he sew through my eyes that I was not sure of which next one he was talking about)
- That’s MSL.
This was 7 months before Phoenix Launched and 16 months before it landed on Mars. So I assumed at this time that this team (Adam Steltzner’s) was NOT in charge of Phoenix EDL.
Now my understanding is that, after Curiosity landing, this very team has no longer any work…but this information came before InSight selection... but the above conversation make me think they are not involved.
So my basic question is: does somebody know who’s in charge of InSight EDL?

[JRehling]

There are a lot of issues on the deliberate-thump and impact sounding of Mars.

Impacts are part of the plan (not like we could do anything to stop them!) and one mission objective is to determine the impactor flux at Mars. Of course, many impacts are filtered out by the atmosphere. Perhaps nearby impacts that don't reach the ground will be detected (that kinetic energy goes somewhere).

Deliberate-thump is not part of the plan. One issue is that the landed hardware has to be set up in time for the thump, and previous landers' moving parts usually haven't gotten moving in the minutes after landing. So there'd be a bit of complexity in getting the thumper to arrive where you want it but after a delay, OR force the seismometer to be deployed very rapidly (which is subject to error; Spirit and Phoenix both had hiccoughs).

Note that Phobos tides will be another form of known stress. These will be much weaker than lunar tides on Earth, but they expect to detect them. Tidal stress is generally reckoned to follow the inverse cube of distance, and Phobos is very close to Mars. However, the equations I've seen may have been derived assuming distance >> planetary radius, which is not the case for Phobos and Mars. In any event, the tides are non-negligible.

[tolis]

Hi All,

On the subject of Phobos tides, one factor that should promote their detectability is that
they occur at a precisely known frequency (since the location of the source - Phobos -
as a function of time and the period of its orbit is known). If one then stacks up the data
over time at the same frequency, the signal would eventually rise out of the noise.

Of course, "eventually" may be a month, a year or longer.

Tolis.

[JRehling]

Here's a piece about the seismometer which will fly on InSight. Given the >4 decade interval, it may not be surprising that it is more sensitive than the lunar seismometers in the ALSEPs. The Viking seismometer was less sensitive than the ALSEPs, as Viking had much more severe mass limits than Apollo.

http://www.kit.edu/visit/pi_2012_11447.php

I suppose that any metrics of the equipment also depend on the planet. How well the local regolith allows the seismometer to couple, and how well the planet propagates waves are factors beyond our control. Also, winds will blow against InSight, which was no concern on the Moon.

[Paolo]

a few (small) pics of the seismometer on the blog of the French team that is developing it
http://ganymede.ipgp.jussieu.fr/gsp-blog/
scroll down to the 1 June (1 juin) entry

[Yooper]

Hi!

Does anyone have a link to the August 20 phone conference when InSight was announced?

Thanks!

[arachnitect]

Hi!

Does anyone have a link to the August 20 phone conference when InSight was announced?

Thanks!

NASA does not, apparently, maintain a public archive of media teleconferences. Thankfully, there appears to be an MP3 here:

http://spaceref.com/podcasts/spacetalk.xml

[rlorenz]

Thanks for confirming that. That met data is basically engineering data aka "noise". But, hopefully it can be useful scientifically as well.

Even with the seismometer sitting on the ground with a wind shield, wind will couple some energy into the ground as it pushes on the lander. Additionally, ground deformations occur as pressure systems migrate across the surface. So ancillary meteorology data is vital to make sense of the seismic measurements (as well as being of interest in its own right). For a review of these issues (and if you want to know the ground motions produced by a Leopard 1 main battle tank...) see http://www.lpl.arizona.edu/~rlorenz/seismology.pdf

[Yooper]

NASA does not, apparently, maintain a public archive of media teleconferences. Thankfully, there appears to be an MP3 here:

http://spaceref.com/podcasts/spacetalk.xml

I'm listening to it now...THANKS a bunch!
Greg.

[Yooper]

Hello – two layperson questions about InSight’s seismometer:

One, will the instrument be able to collect data at night? Or, will the craft’s power budget rule that out?

Two, can someone offer a sense of how sensitive will the seismometer be? How small a Marsquake could it measure (could that measurement be expressed in the Richer scale?)?

Thanks!

[JRehling]

how sensitive will the seismometer be?

This depends quite a bit on Mars itself, both the planet overall, the regolith where the seismometer is emplaced, and how close to the landing site any events happen to be.

The seismometer stories from ALSEP are interesting as a possible comparison. Here, it's written up in quite an accessible form:

http://www.honeysucklecreek.net/msfn_missi...P/hl_alsep.html

The performance of a seismometer is multidimensional: One measures the frequency range, dynamic range, and sensitivity.

Here's some information about InSight's seismometer:

http://www.lpi.usra.edu/meetings/lpsc2012/pdf/1983.pdf

An interesting point there is that they hope to detect impact events with the seismometer, then use orbiters to subsequently identify the precise impact location. That's a very powerful combination if that works.