Timeline for How cold is the Martian sky at night? Or the day for that matter?
Current License: CC BY-SA 4.0
14 events
| when toggle format | what | by | license | comment | |
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| Aug 1, 2020 at 3:57 | comment | added | uhoh | I've linked this page to Could Ingenuity stay warmer at night by landing on (or near) Perseverance's RTG?. In order to have confidence that the helicopter will not drain its battery before morning in order to stay warm, they either had to know do some careful modeling and maybe used some data from Curiosity's thermometers, or simply over-design the insulation around the helicopter. But that might make it get too hot when flying. Hmm... I'm going to think about this further; I think there are several new questions here. | |
| Jun 7, 2018 at 3:08 | history | bounty ended | uhoh | ||
| Jun 7, 2018 at 3:07 | vote | accept | uhoh | ||
| Jun 3, 2018 at 20:03 | comment | added | Tom Spilker | @SF. Often it's not hard to get an instrument on a mission if the total cost will be, say, 3 megabucks. But if the Project Scientist and Project Manager really want to fly a 22 Mbuck instrument for the mission's top science priority, and flying the 3 Mbuck instrument (that addresses a lower science priority) means they'd have to settle for a significantly inferior 19 Mbuck instrument for the top priority objectives, then they'll happily toss the 3 Mbuck instrument. Sometimes it comes down to what the science priorities du jour are. | |
| Jun 3, 2018 at 19:54 | comment | added | Tom Spilker | @SF. You might be surprised at how much being on an interplanetary flight mission can run up the cost of even a simple instrument. The requirements for reliability in the space environment means that inexpensive components have to be replaced by ones that are tested and documented, radiation-tolerant, etc., so a 50-buck instrument in a consumer electronics shop quickly becomes a 500k (or more) instrument. And that's before all the work & redesign involved with instrument/spacecraft compatibility: no electromagnetic interference, untoward mechanical or thermal loads,etc. Adds up to millions! | |
| Jun 3, 2018 at 3:19 | comment | added | SF. | @TomSpilker: in one hand, maybe. On the other hand, strapping a simple IR thermometer to Cutiosity' arm wouldn't be hard, and it could check temperatures of rocks, use it for self-diagnostics, or point at the sky. | |
| Jun 3, 2018 at 2:01 | comment | added | uhoh | @TomSpilker Indeed. I asked this question a few weeks after posting this answer to the question Will suits worn on Mars lose kilograms of “expendable water” each time they are used? I suggested "ice batteries" (i.e. cold packs) left outside could recharge themselves via "...some simple insulation flaps that passively open at night so they can radiate to space..." I asked this question about sky temperature when I started thinking about "recharging" during the day as well. | |
| Jun 2, 2018 at 21:55 | comment | added | Tom Spilker | @SF. The loss of interest in doing those measurements is probably related to the politics of NASA and its government overlords, the executive branch (NASA reports to the Vice President of the US). In the late 1990's there was a lot of discussion at the highest levels of NASA concerning future habitation at Mars, and the infrastructure needed for that, such as in-situ resource utilization (ISRU). That led to interest in rejecting heat from resource-utilizing machines, and thus to radiators and sky temperature. That died off for a while (15-20 years!) but ISRU might be making a comeback. | |
| Jun 2, 2018 at 21:40 | comment | added | Tom Spilker | @uhoh The high sky temperatures in Gere Justus's MarsGRAM 2001, as you point out in your question "...Why the 'hot spot;?", indicate to me that the models Wachter ran did not include an upper limit case, since they apparently didn't include atmospheric heating from a significant dust load near solar noon. | |
| Jun 2, 2018 at 2:22 | comment | added | uhoh | fyi I've just asked What is the science behind the variation of Mars' effective sky temperature with latitude and longitude? Why the “hot spot”? | |
| Jun 2, 2018 at 2:21 | comment | added | uhoh | There's a section on this and Figure 4.4 even shows a plot of "...longwave irradiance at the surface, expressed as sky temperature..." in Mars Global Reference Atmospheric Model 2001 Version (Mars-GRAM 2001): Users Guide which shows mid-latitude values circa 150 to 200K. | |
| Jun 2, 2018 at 1:39 | comment | added | uhoh | I've just asked When will NASA PubSpace really make publicly available most of NASA funded research papers? | |
| Jun 2, 2018 at 1:25 | comment | added | SF. | I like when someone can authoritatively state "we don't know." OTOH it surprises me no mission included such an instrument. I got my IR thermometer off Aliexpress for like $5 and it's the size of an AA battery, display and batteries included. Sure "for space" is not \$5, but even at 10,000x the price it would still be peanuts by space standards, and not a noticeable hit to weight and energy budget either. | |
| Jun 1, 2018 at 21:50 | history | answered | Tom Spilker | CC BY-SA 4.0 |