Author Topic: Mars Exploration Rovers Update  (Read 296531 times)

Offline Kaputnik

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Re: Mars Exploration Rovers Update
« Reply #140 on: 03/09/2011 09:29 pm »
The amount of solar energy
available to Spirit then will increase until the southern Mars summer
solstice in March 2011. If we haven't heard from it by March, it is
unlikely that we will ever hear from it.

Is it game over for Spirit then? :(
"I don't care what anything was DESIGNED to do, I care about what it CAN do"- Gene Kranz

Offline robertross

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Re: Mars Exploration Rovers Update
« Reply #141 on: 03/10/2011 12:13 am »
The amount of solar energy
available to Spirit then will increase until the southern Mars summer
solstice in March 2011. If we haven't heard from it by March, it is
unlikely that we will ever hear from it.

Is it game over for Spirit then? :(

Basically in that position now:

"Spirit's most recent communication was on March 22, 2010. On the possibility that Spirit may yet awaken from a low-power hibernation status, NASA engineers continue to listen for a signal from that rover."

Offline robertross

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Re: Mars Exploration Rovers Update
« Reply #142 on: 03/19/2011 03:00 pm »
Alternatives Have Begun in Bid to Hear from Spirit

March 18, 2011

PASADENA, Calif. -- Hopes for reviving NASA's Spirit Mars rover dimmed further with passage last week of the point at which the rover's locale received its maximum sunshine for the Martian year.

The rover team has tried to contact Spirit for months with strategies based on the possibility that increasing energy availability might wake the rover from hibernation. The team has now switched to communication strategies designed to address more than one problem on the rover. If no signal is heard from Spirit in the next month or two, the team at NASA's Jet Propulsion Laboratory, Pasadena, Calif., will shift to single-rover operations, continuing to operate Spirit's active twin, Opportunity.

"The commands we are sending starting this week should work in a multiple-fault scenario where Spirit's main transmitter is no longer working and the mission clock has lost track of time or drifted significantly," said JPL's John Callas, project manager for Spirit and Opportunity.

Spirit landed on Mars Jan. 4, 2004 Universal Time (Jan. 3, Pacific Time) for a mission designed to last for three months. After accomplishing its prime-mission goals, Spirit worked for more than five years in bonus-time extended missions.

Spirit has not communicated since March 22, 2010. Power output from its solar array had been waning prior to that, and the rover had been expected to go into a low-power hibernation mode. With drive motors on two of its six wheels no longer working, Spirit had been unable in preceding months to maneuver much in its sand-trap location. The rover could not get to a favorable tilt for its solar panels as Martian winter approached.

During the Martian winter with most heaters turned off, Spirit experienced colder internal temperatures than in any of its three previous winters on Mars. The cold could have damaged any of several electronic components that, if damaged, would prevent reestablishing communication with Spirit.

However, attempts to regain contact have continued for more than eight months in the possibility that the seasonal increase in solar energy available at Spirit's location would revive the rover. NASA's Deep Space Network of antennas in California, Spain and Australia has been listening for Spirit daily. The rover team has also sent commands to elicit a response from the rover even if the rover has lost track of time, or if its receiver has degraded in frequency response.

The available solar energy at Spirit's site was estimated to peak on March 10. Revised commanding began March 15, including instructions for the rover to be receptive over UHF relay to hailing from the Mars orbiters for extended periods of time and to use a backup transmitter on the rover.

Spirit and Opportunity both have made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life. Opportunity landed three weeks after Spirit.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Science Mission Directorate, Washington.

http://www.jpl.nasa.gov/news/news.cfm?release=2011-087

Offline Lee Jay

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Re: Mars Exploration Rovers Update
« Reply #143 on: 03/19/2011 03:15 pm »
"Spirit's most recent communication was on March 22, 2010. On the possibility that Spirit may yet awaken from a low-power hibernation status, NASA engineers continue to listen for a signal from that rover."

What a piece of junk!  It only worked for 24 times longer than it was supposed to!

Hope my boss doesn't hear about that.   ;)

Nice job, Spirit!

Offline aceshigh

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Re: Mars Exploration Rovers Update
« Reply #144 on: 04/18/2011 01:37 pm »
what better way to surpass expectations and get more funding, than to lower expectations to the minimum?

I have my doubts the scientists who created the rovers really expected them to last for only a few months, as they announced.


anyway, can someone help me?

I run across a conspirationist who thinks its "weird" that the rovers send no videos, only images, since they are so easy to manipulate.

I told him the bandwidth is very limited and to increase the bandwidth, they would need more power, which is actually very limited, since they run on solar power in a place with far less sun energy than Earth.

Does anyone has more info about the subject? How much energy you need for what bandwidth, etc?

Offline Jim

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Re: Mars Exploration Rovers Update
« Reply #145 on: 04/18/2011 02:18 pm »
what better way to surpass expectations and get more funding, than to lower expectations to the minimum?

I have my doubts the scientists who created the rovers really expected them to last for only a few months, as they announced.


anyway, can someone help me?

I run across a conspirationist who thinks its "weird" that the rovers send no videos, only images, since they are so easy to manipulate.

I told him the bandwidth is very limited and to increase the bandwidth, they would need more power, which is actually very limited, since they run on solar power in a place with far less sun energy than Earth.

Does anyone has more info about the subject? How much energy you need for what bandwidth, etc?

It is more than just that

Not just bandwidth.  Increased Data storage onboard, since it can't be realtime broadcast. 

UHF relay is intermittent due to infrequent overpasses of relay spacecraft (MRO & Mars Odyssey).   Xband direct would require a 2 axis stabilized antenna.

It needs more power.  It can not rove, photo and transmit at the same time.  Hence there is no reason for video, if the photos are taken while stationary.

There are many more other reasons.
« Last Edit: 04/18/2011 02:18 pm by Jim »

Online Galactic Penguin SST

Re: Mars Exploration Rovers Update
« Reply #146 on: 04/18/2011 02:56 pm »
what better way to surpass expectations and get more funding, than to lower expectations to the minimum?

I have my doubts the scientists who created the rovers really expected them to last for only a few months, as they announced.


anyway, can someone help me?

I run across a conspirationist who thinks its "weird" that the rovers send no videos, only images, since they are so easy to manipulate.

I told him the bandwidth is very limited and to increase the bandwidth, they would need more power, which is actually very limited, since they run on solar power in a place with far less sun energy than Earth.

Does anyone has more info about the subject? How much energy you need for what bandwidth, etc?

It is more than just that

Not just bandwidth.  Increased Data storage onboard, since it can't be realtime broadcast. 

UHF relay is intermittent due to infrequent overpasses of relay spacecraft (MRO & Mars Odyssey).   Xband direct would require a 2 axis stabilized antenna.

It needs more power.  It can not rove, photo and transmit at the same time.  Hence there is no reason for video, if the photos are taken while stationary.

There are many more other reasons.

Hi, you may try to find the book Roving Mars by MER's PI Steve Squyres (ISBN 1-4013-0851-1). It's a great book of how the whole project goes from the first concepts (in 1997!) to the first year of the project (2005), with many good descriptions of the designing, building and running of the whole program. If you need to debunk your friend's conspiracy, this should be enough. In addition, it's a great read too!
Hopefully this will helps. :)
Astronomy & spaceflight geek penguin. In a relationship w/ Space Shuttle Discovery. Current Priority: Chasing the Chinese Spaceflight Wonder Egg & A Certain Chinese Mars Rover

Offline aceshigh

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Re: Mars Exploration Rovers Update
« Reply #147 on: 04/18/2011 03:31 pm »
what about my little conspiracy? The one where I think NASA and the scientists working on the Mars rovers probably knew the rovers WOULD work more than only 6 months, but they set the bar pretty low so anything more would be an overachievement resulting in more funds (you see, Congressmen? NASA can be efficient!)

Any probability that expectations were set much lower than what we should really expect from the rovers, so their success was even more stupendous than they should be already??


I mean... if the scientists said "we expect the rovers to function for at least 3 years), the chances of them failing before that and be considered a failure would be LARGE.

if you set from the start a short date validity, the chances they will surpass that date and thus be considered a major success is LARGE.

Offline Jim

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Re: Mars Exploration Rovers Update
« Reply #148 on: 04/18/2011 03:50 pm »
what about my little conspiracy?

Not true

Offline Lee Jay

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Re: Mars Exploration Rovers Update
« Reply #149 on: 04/18/2011 03:53 pm »
what about my little conspiracy? The one where I think NASA and the scientists working on the Mars rovers probably knew the rovers WOULD work more than only 6 months, but they set the bar pretty low so anything more would be an overachievement resulting in more funds (you see, Congressmen? NASA can be efficient!)

The short expectation was primarily based on the expectation of accumulation of dust on the solar cells.  I remember one scientist on the project saying something to the effect that, "we know they are going to be born with a terminal illness".  What they didn't expect were these "cleaning events" which seem to happen intermittently and substantially clean the panels.  I haven't been following closely enough to know if they've conclusively determined what causes these cleaning events, be it a gust of wind or one of those Mars whirlwinds passing over the rovers or something else.

Note that Curiosity (Mars Science Laboratory) is expected to operate for one Martian year or more because it's RTG doesn't suffer from the dust effect that can hinder electricity production from the solar cells.

Offline brihath

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Re: Mars Exploration Rovers Update
« Reply #150 on: 04/18/2011 04:00 pm »
what about my little conspiracy? The one where I think NASA and the scientists working on the Mars rovers probably knew the rovers WOULD work more than only 6 months, but they set the bar pretty low so anything more would be an overachievement resulting in more funds (you see, Congressmen? NASA can be efficient!)

Any probability that expectations were set much lower than what we should really expect from the rovers, so their success was even more stupendous than they should be already??


I mean... if the scientists said "we expect the rovers to function for at least 3 years), the chances of them failing before that and be considered a failure would be LARGE.

if you set from the start a short date validity, the chances they will surpass that date and thus be considered a major success is LARGE.

The longer than planned longevity for the MER's is not all that unique.  Many comsats and intel satellites have lasted long beyond their planned lifetimes, providing a cost benefit to the operators.  Also, both the Pioneer and Voyager probes lasted far beyond their lifetimes.

Designing equipment that is robust as possible given weight and cost constraints is probably the common thread, not conspiracy.

Offline aceshigh

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Re: Mars Exploration Rovers Update
« Reply #151 on: 04/18/2011 05:08 pm »
what about my little conspiracy?

Not true

why?

was it just luck that they worked 24 times longer than expected? Most conspiracies theories fall because of Occam´s Razor. Big conspiracies are less probable to occur or be hidden than what really ocurred (like sending men to the moon)

but a small "conspiracy" involving only a few people that could properly determine how much time the rovers would be able to last on Mars surface, its probably more probable an explanation than they outlasting the initial estimates by 24 times!

unless a better explanation exists. And it has been provided by Lee Jay. Thanks.


@Brihath: my use of the word "conspiracy" may not even have been the best one. Maybe we could better define what a conspiracy is.

If many comsats and intel satellites survive for much longer than their planned lifetimes, that means the space industry in general sets the bar LOW. They are either pessimistic, dont understand their own devices and thus cant properly calculate how long their will last (very unlikely), or know that setting a low bad, and then far exceeding the expectations is a very good thing for an industry that survives on low numbers of high value products and services.

Offline Jim

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Re: Mars Exploration Rovers Update
« Reply #152 on: 04/18/2011 05:20 pm »

but a small "conspiracy" involving only a few people that could properly determine how much time the rovers would be able to last on Mars surface, its probably more probable an explanation than they outlasting the initial estimates by 24 times!

Yes, it is luck!

No, there is no conspiracy and it is not a "few" people, it is many.  The 90 day mission life was design requirement and not a prediction.  It determined the minimal lifespan of the rovers.  The design requirement set a minimum level to how robust the parts were made.  It also determined the testing levels. The cost ceiling of the project and weight constraints also set a ceiling on robustness.  After the 90 requirement was met for parts, weight and cost also come into play.



Offline Jim

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Re: Mars Exploration Rovers Update
« Reply #153 on: 04/18/2011 05:37 pm »

If many comsats and intel satellites survive for much longer than their planned lifetimes, that means the space industry in general sets the bar LOW. They are either pessimistic, dont understand their own devices and thus cant properly calculate how long their will last (very unlikely), or know that setting a low bad, and then far exceeding the expectations is a very good thing for an industry that survives on low numbers of high value products and services.

No, it does not.    There are just as many with shorter lifetimes.  Look up bell curve.

Offline iamlucky13

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Re: Mars Exploration Rovers Update
« Reply #154 on: 04/18/2011 11:33 pm »
Aceshigh - See if your local library has Roving Mars and give it a read, or if you're really interested, buy a copy.

When finished, you will really understand that they designed them with a notional lifetime of 1 year, but reasonably expected they would not last that long because of dust exposure.

For that reason, they baselined the mission for 90 days, as they believed they get enough solar power in the worst case dust scenarios to last at least that long. If they didn't last at least that long, the mission would be considered a partial failure.

They expected they would last that long, however, and their budget included several mission extensions. First an additional 90 days. After those 6 months were up, they would assess the condition and approve up to another 6 months.

All of that was in the mission plan ahead of time.

After 1 year, they considered the health of the rovers speculative, but were hoping to be able to ask Congress for a special appropriation to keep funding operations if it seemed possible.

They were fortunate in that the weather turned out to be favorable after landing. However, once they reached two years of operations, they were genuinely beyond what they had expected to achieve.

The dust devils that turned out to occasionally clear settled dust off the solar panels was a curve ball. No one expected that.

Mechanically they performed better than expected in most regards, too. That's part good design, and part luck. No one intends for their design to fail, but in complex robots, you usually expect something unseen to jump up and bite you. That hasn't really happened.

Offline iamlucky13

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Re: Mars Exploration Rovers Update
« Reply #155 on: 04/18/2011 11:40 pm »
There are many more other reasons.


Including the lack of perceived need. There was minimal value to video.

Then they started seeing dust devils in the stills from the MER's.

MSL will have low framerate (10 fps, I think) video in no small part to be able to study the dust devils better.


Oh...I forgot in my other post:

Lowballing performance estimates so you can wow people later (the "Scotty" principal) only works to a very limited degree.

If you lowball what you think you can achieve, and another proposal team doesn't, Congress is going to say, "These guys can accomplish twice as much for the same price. Try again next time."

You'll never get the chance to cash in on the under-promise, over-deliver glory.

Offline hop

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Re: Mars Exploration Rovers Update
« Reply #156 on: 04/19/2011 03:20 am »
was it just luck that they worked 24 times longer than expected?
No, you aren't understanding the 90 day requirement.

If you build car that must (with say 99% certainty) last for 100,000 miles, how long do you think the average example will last ?

The MERs were built to last at least 90 days, with as much certainty as possible, in an environment with a great deal of uncertainty.

They also got lucky at a number of points, either one could have died years ago with only minor differences in circumstances.

Offline notsorandom

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Re: Mars Exploration Rovers Update
« Reply #157 on: 04/19/2011 03:55 am »
Let me be another to recommend the book Roving Mars. It has been a while since I read it but if I remember correctly there was a discussion on getting the most solar cell area. The thinking was that the mission would likely end because of dust build up before something else might kill the rovers. Thus the more solar cells the rover had the longer the mission could go on. They had quite cleverly figured out how to fold additional panels in. Also gave the rovers a futuristic swept wing look as Squires points out in the book.

Aside from the cleaning events and the power issues it is still remarkable that they have held on this long. Mars is covered in very fine dust that can work its way into the rovers and abrade the machinery. It is also very cold. After a couple hundred days the rovers were solidly into borrowed time as other things might break down and end the rovers.

I would also recommend the book "Sojourner: An Insider's View of the Mars Pathfinder Mission" It has a similar feel to Squire's book but is about the MER's ancestor.

Offline iamlucky13

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Re: Mars Exploration Rovers Update
« Reply #158 on: 04/20/2011 01:05 am »
^ Your memory is correct.

To pre-empt another common question, they did also consider wipers and blowers to remove dust, but concluded the complexity of packaging, deploying them, ensuring they were reliable, and the impact to mass and cost were less favorable than increasing solar panel area to deal with the gradual reduction of power due to dust.

And I might add, the Mars Exploration Rovers are a beautiful example of a functional design choice leading to appealing aesthetics. The swept foldout panels that resulted partially from the tetrahedral descent stage shape make them look far sleeker and sexier than pretty much any other rover so far built or conceived (in my opinion, including ATHLETE)

Offline jacqmans

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Re: Mars Exploration Rovers Update
« Reply #159 on: 05/05/2011 08:10 am »
News release: 2011-133                                                                    May 4, 2011

Mars Tribute Marks Memories of Shepard's Flight

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-133&cid=release_2011-133

The team exploring Mars via NASA's Opportunity rover for the past seven years has informally named a Martian crater for the Mercury spacecraft that astronaut Alan Shepard christened Freedom 7. On May 5, 1961, Shepard piloted Freedom 7 in America's first human spaceflight.

The team is using Opportunity this week to acquire images covering a cluster of small, relatively young craters along the rover's route toward a long-term destination. The cluster's largest crater, spanning about 25 meters (82 feet), is the one called "Freedom 7." The diameter of Freedom 7 crater, about 25 meters (82 feet), happens to be equivalent to the height of the Redstone rocket that launched Shepard's flight.

"Many of the people currently involved with the robotic investigations of Mars were first inspired by the astronauts of the Mercury Project who paved the way for the exploration of our solar system," said Scott McLennan of the State University of New York at Stony Brook, who is this week's long-term planning leader for the rover science team. Shepard's flight was the first of six Project Mercury missions piloted by solo astronauts.

An image of Freedom 7 crater taken this week is online at: http://photojournal.jpl.nasa.gov/catalog/PIA13988.

Rover team member James Rice of NASA Goddard Space Flight Center, Greenbelt, Md., said, "The first 50 years of American manned spaceflight have been built upon immeasurable courage, dedication, sacrifice, vision, patriotism, teamwork and good old-fashioned hard work, all terms that embody and define the United States and her people. Alan Shepard's brave and historic 15-minute flight in Freedom 7 put America in space, and then a scant eight years later, Americans were standing upon the surface of the moon." Shepard himself would later walk on the moon when he commanded the Apollo 14 mission in early 1971, less than 10 years after his Freedom 7 flight. He died on July 21, 1998.

By taking advantage of seeing many craters of diverse ages during drives toward major destinations, the Opportunity mission is documenting how impact craters change with time. The cluster that includes Freedom 7 crater formed after sand ripples in the area last migrated, which is estimated to be about 200,000 years ago.

"This cluster has about eight craters, and they're all the same age," said Matt Golombek, rover team member at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "They're from an impactor that broke up in the atmosphere, which is quite common."

Opportunity and its twin, Spirit, completed their three-month prime missions on Mars in April 2004. Both rovers continued for years of bonus, extended missions. Both have made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life. Spirit has not communicated with Earth since March 2010. Opportunity remains active. It has driven 28.6 kilometers (17.8 miles) total on Mars, including 1.9 kilometers (1.2 miles) since leaving "Santa Maria" crater on March 24, 2011, after studying that crater for three months.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for the NASA Science Mission Directorate, Washington. More information about the rovers is online at: http://www.nasa.gov/rovers .

Jacques :-)

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