Mars Rovers power dwindling...why?

Hi....

Hope this isn't too silly a question...but lately, I've been reading
that the Martian Rovers are beginning to have less power available to
them because of dust that is accumulating on their solar cells. Is that
right? It's hard to believe that such a problem could not have been
forseen and handled. And, if so, maybe NASA would build in a can of air
(- to blow off the dust, or maybe have a built-in shaker to shake the
dust off the solar cells, etc. What am I missing?

Thanks...

Ken

Dear Ken:

"Ken" wrote in message
. ..
Hi....

Hope this isn't too silly a question...but lately, I've been reading
that the Martian Rovers are beginning to have less power available to
them because of dust that is accumulating on their solar cells. Is that
right? It's hard to believe that such a problem could not have been
forseen and handled. And, if so, maybe NASA would build in a can of air
(- to blow off the dust, or maybe have a built-in shaker to shake the
dust off the solar cells, etc. What am I missing?

Could be static electricity. The ambient humidity is really low, and there
is friction between dissimilar materials...

David A. Smith

"K" == Ken writes:

K I've been reading that the Martian Rovers are beginning to have
K less power available to them because of dust that is accumulating
K on their solar cells. Is that right? It's hard to believe that such
K a problem could not have been forseen and handled. And, if so,
K maybe NASA would build in a can of air (- to blow off the dust,
K or maybe have a built-in shaker to shake the dust off the solar
K cells, etc. What am I missing?

Nothing. This problem was forseen. That's why the rovers have a
limited mission (90 days).

David Smith has posted one aspect of dust removal already.

I'll add that, from the mission standpoint, trying to keep the rovers
running longer is a cost/benefit analysis. Every gram of a Dust
Removal System that you put on the rover is one less gram that can be
used for scientific instrumentation. Moreover, each additional system
on a rover adds more possible failure modes. What if the can of air
is punctured by a micrometeorite at some point? What if the shaker
breaks or freezes during mid-shake? What if ...?

--
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On 03 Mar 2004 10:40:31 -0500, Joseph Lazio wrote:

"K" == Ken writes:

K I've been reading that the Martian Rovers are beginning to have
K less power available to them because of dust that is accumulating
K on their solar cells. Is that right? It's hard to believe that such
K a problem could not have been forseen and handled. And, if so,
K maybe NASA would build in a can of air (- to blow off the dust,
K or maybe have a built-in shaker to shake the dust off the solar
K cells, etc. What am I missing?

Nothing. This problem was forseen. That's why the rovers have a
limited mission (90 days).

David Smith has posted one aspect of dust removal already.

What if there is a windstorm ? would the net result be more or less dust on
the panels?

--

Boris Mohar

"Boris Mohar" wrote in message
...
On 03 Mar 2004 10:40:31 -0500, Joseph Lazio
wrote:

"K" == Ken writes:

K I've been reading that the Martian Rovers are beginning to have
K less power available to them because of dust that is accumulating
K on their solar cells. Is that right? It's hard to believe that such
K a problem could not have been forseen and handled. And, if so,
K maybe NASA would build in a can of air (- to blow off the dust,
K or maybe have a built-in shaker to shake the dust off the solar
K cells, etc. What am I missing?

Nothing. This problem was forseen. That's why the rovers have a
limited mission (90 days).

David Smith has posted one aspect of dust removal already.

What if there is a windstorm ? would the net result be more or less dust
on
the panels?

Depends on the static-electrical charges involved.
If the increased friction increases the static
charge sufficiently - that might overcome the pressure
of the wind and might even result in a net increase in
dust.
Not necessarily likely, but possible.

On a sunny day (03 Mar 2004 10:40:31 -0500) it happened Joseph Lazio
wrote in :

Every gram of a Dust
Removal System that you put on the rover is one less gram that can be
used for scientific instrumentation.
You have a math problem.
With the wind shield wiper added, the mission could last indefinite.
Now that interesting stuff is there, and hear millions crying 'save Hubble',
see what would you give to drive over those hills and find more.
It is infinity against 90 days.

Joseph Lazio wrote in message ...
"K" == Ken writes:

K I've been reading that the Martian Rovers are beginning to have
K less power available to them because of dust that is accumulating
K on their solar cells. Is that right? It's hard to believe that such
K a problem could not have been forseen and handled. And, if so,
K maybe NASA would build in a can of air (- to blow off the dust,
K or maybe have a built-in shaker to shake the dust off the solar
K cells, etc. What am I missing?

Nothing. This problem was forseen. That's why the rovers have a
limited mission (90 days).

David Smith has posted one aspect of dust removal already.

I'll add that, from the mission standpoint, trying to keep the rovers
running longer is a cost/benefit analysis. Every gram of a Dust
Removal System that you put on the rover is one less gram that can be
used for scientific instrumentation. Moreover, each additional system
on a rover adds more possible failure modes. What if the can of air
is punctured by a micrometeorite at some point? What if the shaker
breaks or freezes during mid-shake? What if ...?

They should have sent the LASERS:

http://www.thebatt.com/news/2004/03/...e-624097.shtml

"JP" == Jan Panteltje writes:

JP On a sunny day (03 Mar 2004 10:40:31 -0500) it happened Joseph
JP Lazio wrote in
JP :

Every gram of a Dust Removal System that you put on the rover is
one less gram that can be used for scientific instrumentation.

JP You have a math problem. With the wind shield wiper added, the
JP mission could last indefinite. Now that interesting stuff is
JP there, and hear millions crying 'save Hubble', see what would you
JP give to drive over those hills and find more. It is infinity
JP against 90 days.

You snipped the part of my answer in which I dealt with this
possibility. Every additional system added to the rover increases the
number of failure modes. You might very well end up with two rovers
on the surface, with broken solar cells because the the Dust Removal
System malfunctioned. In this case you'd get no science return and
lots of press complaining, "NASA wastes another $1 billion on Mars
missions."

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

On a sunny day (04 Mar 2004 11:40:24 -0500) it happened Joseph Lazio
wrote in :

"JP" == Jan Panteltje writes:

JP On a sunny day (03 Mar 2004 10:40:31 -0500) it happened Joseph
JP Lazio wrote in
JP :

Every gram of a Dust Removal System that you put on the rover is
one less gram that can be used for scientific instrumentation.

JP You have a math problem. With the wind shield wiper added, the
JP mission could last indefinite. Now that interesting stuff is
JP there, and hear millions crying 'save Hubble', see what would you
JP give to drive over those hills and find more. It is infinity
JP against 90 days.

You snipped the part of my answer in which I dealt with this
possibility. Every additional system added to the rover increases the
number of failure modes. You might very well end up with two rovers
on the surface, with broken solar cells because the the Dust Removal
System malfunctioned. In this case you'd get no science return and
lots of press complaining, "NASA wastes another $1 billion on Mars
missions."
The MTBF would scale, but not that much, very few components are needed
for a whiper.
The fact that a whiper would destroy the solar cells, well if you keep it locked
until day 90 (or when needed), then blow the bolts, you can only win.
That is why I left out the repeat of your argument.
In electronics -more components = more errors- is in fact not true.
If the whiper can keep it going after 90 days it is: 10 more components,
nnn x 10 times lifetime.
MTBF is not used these days the same way as even 10 or 20 years ago.
JP

"JP" == Jan Panteltje writes:

JP On a sunny day (03 Mar 2004 10:40:31 -0500) it happened Joseph
JP Lazio wrote in
JP :

Every gram of a Dust Removal System that you put on the rover is
one less gram that can be used for scientific instrumentation.

JP You have a math problem. With the wind shield wiper added, the
JP mission could last indefinite.

If the dust is electrostatically attracted to the surface of the solar cells
- all the wind shield wiper would do is scratch the surface and reduce
its capability all that much quicker. A brush wouldn't necessarily help.
It might merely increase the electrostatic attraction. An air blower
for the surface area of Rover solar panels in such a low pressure
environment is considerably more complex than it might seem at
first glance. Especially when every gram of mass counts heavily
and the engineers barely had enough time to build and test what they
actually sent.

Now that interesting stuff is
JP there, and hear millions crying 'save Hubble', see what would you
JP give to drive over those hills and find more. It is infinity
JP against 90 days.

It is not infinity under any circumstances. Quit bull****ting.
Dust on the solar arrays are not the only limiting factor.