Sundial sitting on solar panels, A question about power requirements |
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Sundial sitting on solar panels, A question about power requirements |
 Sep 2 2006, 03:03 PM
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#1
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Member  Group: Members Posts: 147 Joined: 14-April 06 From: Berlin Member No.: 744  |
I am currently digging in the Planetary Radio archives and heared Bill Nye saying that the Mars sundial sitting on the solar panels takes about 1 to 2 percent of power by covering them. The sundial itself is of course a great outreach idea and probably does not affect the mission as Bill said. BUT: what if the 2 percent were the LAST 2 percent left? What is the minimum power requirement for MERs? And namely a) for being able to rove
 for being able to use the RAT c) for being able to sit calmly and just send data to the orbiters. No intention to question the "Two Worlds One Sun" thing, I really love it. Just made me curious about the power as it might be relevant in speculations about their expected lifespan.
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Sep 2 2006, 03:29 PM
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#2
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Member Group: Members Posts: 198 Joined: 29-June 05 Member No.: 421 |
The "sundials" are the most photographed things on mars for a reason -- their major function is as the calibration targets for the pancam. So, yes, they take up space and weight and reduce the surface area available for solar energy generation. But they add a lot to the scientific value of all the images that are coming down. They allow scientists to translate the "pretty pictures" into actual spectrographically calibrated measurements. So this isn't just wasted space...
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Sep 2 2006, 04:01 PM
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#3
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 Member Group: Members Posts: 577 Joined: 5-November 04 From: Denmark Member No.: 107 |
And the HGA and the PMA takes up much more than 2 percent
 
-------------------- "I want to make as many people as possible feel like they are part of this adventure. We are going to give everybody a sense of what exploring the surface of another world is really like"
- Steven Squyres |
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Sep 3 2006, 04:31 PM
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#4
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Member Group: Members Posts: 147 Joined: 14-April 06 From: Berlin Member No.: 744 |
And I was not suggesting to toss'em as worthless but asking what the MERs could do with only 2% of power left
 Could they at least send some bits to the orbiters?
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Sep 3 2006, 04:46 PM
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#5
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 Senior Member Group: Members Posts: 2562 Joined: 14-February 06 From: Very close to the Pyrénées Mountains (France) Member No.: 682 |
QUOTE (karolp @ Sep 3 2006, 06:31 PM)  And I was not suggesting to toss'em as worthless but asking what the MERs could do with only 2% of power left Could they at least send some bits to the orbiters?Do NOTHING and wait untill the batteries charge the next day  I talked will Bill Nye on the very day of Spirit landing and he was very proud of the sundial be in fact a by product of the calibration target. -------------------- |
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Sep 3 2006, 04:47 PM
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#6
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 Administrator Group: Chairman Posts: 13244 Joined: 8-February 04 Member No.: 1 |
2% of 280 Whrs = 5.6 Whrs...
Via UHF - data costs about 0.8 Whr / Mbit - so you could get perhaps 7 Mbits of data home via UHF But of course, with onlly 5.6 Whrs - you've not got enough to warm up some instruments to take data to fill that 7 Mbits However - to put this into some sort of context.. Shadowing causes losses of up to around 20% per sol Doug |
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Sep 4 2006, 04:12 AM
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#7
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Member Group: Members Posts: 477 Joined: 2-March 05 Member No.: 180 |
But is the "mast" portion of the sundial truly necessary? Aren't the colored portions, mirrors, and B&W circles the truly important parts?
The real problem is that the fans aren't good enough. "Mars is very dusty; it was thought that dust coating the solar panels may kill the rovers by choking out the sunlight. Designers worried about it so much, the rovers actually have small fans designed to blow dust off the panels. But the fans have gotten a boost."  
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Sep 4 2006, 05:00 AM
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#8
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Junior Member Group: Members Posts: 35 Joined: 8-July 05 Member No.: 432 |
QUOTE (Jeff7 @ Sep 4 2006, 12:12 AM) The real problem is that the fans aren't good enough. You do know that the last part about DD is going to drive our " Administrator" nuts...
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Sep 4 2006, 07:26 AM
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#9
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Senior Member Group: Members Posts: 2562 Joined: 14-February 06 From: Very close to the Pyrénées Mountains (France) Member No.: 682 |
QUOTE (bergadder @ Sep 4 2006, 07:00 AM) You do know that the last part about DD is going to drive our " Administrator" nuts... That's old story now! DD stuffs are buried in concrete under a shed
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Sep 4 2006, 07:29 AM
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#10
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Administrator Group: Chairman Posts: 13244 Joined: 8-February 04 Member No.: 1 |
QUOTE (Jeff7 @ Sep 4 2006, 05:12 AM) But is the "mast" portion of the sundial truly necessary? Yup - by casting a shadow onto the black/grey rings it allows one to calculate the direct illumination and indirect illumination properties And the times when the gnomen ( to give it a technical name ) might cast shadows on the arrays are only very close to sunrise and sunset - a time when the angle if incidence between sun and array is such that you're barely going to drop any power at all. Doug |
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Sep 4 2006, 02:37 PM
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#11
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Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
QUOTE (Jeff7 @ Sep 3 2006, 11:12 PM) The real problem is that the [ the rovers actually have small fans designed to blow dust off the panels.[/b] But the fans have gotten a boost." I learned it too late!!!  I haven't tought that MER has a small fan pointing to sundial? I haven't see it on the picture? I have enclosed the picture which shows sundial and their blowers at right and left sides. Correct me!
Rodolfo |
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Sep 4 2006, 03:20 PM
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#12
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Administrator Group: Chairman Posts: 13244 Joined: 8-February 04 Member No.: 1 |
No no - there ARE no blowers on the rovers - that's the point
What you point out are the pyrotechnic bolts that held the solar arrays together before the thing deployed on Sol 1 Doug |
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Sep 4 2006, 04:40 PM
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#13
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Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
QUOTE (djellison @ Sep 4 2006, 10:20 AM) No no - there ARE no blowers on the rovers - that's the point What you point out are the pyrotechnic bolts that held the solar arrays together before the thing deployed on Sol 1 Doug Good! They were referring to the wind as the blower! Rodolfo |
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Sep 4 2006, 04:55 PM
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#14
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Member Group: Members Posts: 477 Joined: 2-March 05 Member No.: 180 |
QUOTE (djellison @ Sep 4 2006, 03:29 AM) Yup - by casting a shadow onto the black/grey rings it allows one to calculate the direct illumination and indirect illumination properties And the times when the gnomen ( to give it a technical name ) might cast shadows on the arrays are only very close to sunrise and sunset - a time when the angle if incidence between sun and array is such that you're barely going to drop any power at all. Doug That works for me then. The entire sundial stays.
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Sep 5 2006, 12:51 PM
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#15
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 Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
QUOTE (climber @ Sep 3 2006, 12:46 PM) Do NOTHING and wait untill the batteries charge the next day I talked will Bill Nye on the very day of Spirit landing and he was very proud of the sundial be in fact a by product of the calibration target. The sundial was the very first object image radioed to Earth by Spirit after it landed on Mars. Not quite sure if they used the same target with Opportunity's first image. -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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