Dec 4th News Conference Options

[sci44]

But we may need to delay Maven to pay for MSL. There's a hole in my bucket, dear Liza.. :-)

(Edit: There's a hole in my Budget, dear Liza..)

[mcaplinger]

ESA did ask NASA for help trying to talk to Beagle with MGS, so I would guess the ESA would gladly reciprocate.

There's a big difference between a one-off, short term activity and ongoing operations for years. I'm not sure what kind of capability MEx would even have for that given its elliptical orbit.

[djellison]

But we may need to delay Maven to pay for MSL.

THat wasn't mentioned - infact, Maven was still explicitly stated with its orig. launch date. Of course, that may change - but then, for no relay - you're asking for the failure of Mars Odyssey, Mars Express, MRO AND the failure of Maven to launch on time. That's a LOT of 'ifs'.

Doug

[mcaplinger]

Yeah, I've little doubt that, barring some really really bone-headed error, MRO will be around when MSL lands.

It should be noted that MRO had a failure in its telecom system in 2006 which rendered its X-band downlink single-string, so it is one amplifier away from losing the high-gain X-band downlink, and the Ka-band downlink is also suspect though it might be a usable backup. See "In-Flight Anomalies and Lessons Learned from the. Mars. Reconnaissance Orbiter Mission", Todd. J. Bayer, 2008 IEEE Aerospace Conference.

Of course, there's no explicit lifetime for electronics, so MRO could keep going for many years anyway.

[elakdawalla]

I just got an official reply to my question from Dwayne Brown, the PAO for SMD.

The orbiting assets that are expected to be available to support MSL operations when it arrives at Mars (on the revised schedule) include MRO, Mars Express, and Mars Odyssey. Although two years later, it is still expected that these orbiters will be in place and available for communications relay support for MSL.

Having multiple relay-capable orbiters in place allows the continuation of MSL support if one (or even two) of them should become inoperable. In the very unlikely event that all three orbiters should become unable to provide comm relay support, the MSL rover still has the ability to utilize direct-to-Earth (DTE) communications. Albeit slower, the MSL mission could be completed utilizing the DTE link only.

[OWW]

The MSL mission could be completed utilizing the DTE link only.

To me, this sounds like: "The Galileo mission could be completed utilizing the LGA link only."

[mars loon]

Overall I was encouraged by the decisions and progress announced at the press conference.

The mantra is "Failure is not an option" for this Flagship mission. The MSL team will do what it takes to be successful to the best of their ability. we cant ask for more.

These are difficult projects by design, so we attain valuable new science and technology. As they mentioned: The easy things have been done and we wont learn much by repeating that.

I was lucky to ask questions at the end. And i'm very encouraged that Ed Weiler said NASA will cooperate with ESA for future Mars missions. In response he said very likely this could include EXO MARS in a 2016 launch opportunity. The odds of a 2016 launch of something to mars have significantly increased compared to a few weeks ago

ken

[sci44]

So it sounds like they can use MEX too. I did have the idea I read (at the time) that Beagle was going to use MGS/MO for long term comms too..

To me, this sounds like: "The Galileo mission could be completed utilizing the LGA link only."

It would be rather better than that - it would be a high gain antennea, all be it direct DSN comms. The low gain on Galileo was 160 bits/sec (up from 16bits thanks to DSN), vs 134 Kbits/sec for high gain. It will be less, but not 1000 times less!

However there is a good point in there - doesn't MSL plan to generate much more data than MER? In that case having MRO there will make a big difference - the others have much more modest computing/transmission capacities..

[PaulM]

Does the two Year delay change the time of Year at which MSL would land at Southern Hemisphere landing sites?

I ask the question because I understand that if MSL had landed in 2010 at the Southern Hemisphere Eberswalde and Holden crater sites then the landing would have been in the depths of Winter and MSL might have been virtually immovable for the 6 months following the landing.

Does landing in 2012 move the time of landing in Southern sites to a more favourable season of the Year?

[mcaplinger]

[DTE data rate] will be less, but not 1000 times less!

True. Assuming it scales like MER does, DTE will only (!) be about 10-15x slower than relay (as far as I can tell, MER DTE rates are around 20Kbps maximum, while the Odyssey UHF is being run at 256K.)

[ElkGroveDan]

True. Assuming it scales like MER does, DTE will only (!) be about 10-15x slower than relay (as far as I can tell, MER DTE rates are around 20Kbps maximum, while the Odyssey UHF is being run at 256K.)

Any idea how long a typical DTE window or session is?

[djellison]

MER passes were typically 30 - 90 minutes, and MER peaked at 16.6 kbps via its HGA, so 59 Mbits/hour at that rate.

Doug

[ElkGroveDan]

True, but you had an orbiting satellite which has a relative velocity of it's own involved. I would intuitively expect that the DTE sessions would be longer.

[mcaplinger]

I would intuitively expect that the DTE sessions would be longer.

Certainly. A typical UHF pass is only 5-10 minutes long (satellite rise to set), whereas a DTE pass in theory could be for as long as the Earth was in view, less DSN station handoff. MER DTE passes are as short as they are for power and thermal reasons. DTE is much less efficient than relay on an energy/bit basis, and that's probably the big disadvantage of DTE.

[djellison]

That is DTE session.

UHF sessions with orbiters are 10-15 minutes, 128 or 256kbps, and anything from 1 to about 150 Mbits