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Spirit Rover Nightshot 'object'?

  1. Mar 16, 2004 #1
    Last night I was looking over some of the raw images taken by the Spirit rover on the JPL website. Particularly here: http://origin.mars5.jpl.nasa.gov/gallery/all/spirit_p067.html
    Sol 67 (March 11) Spirit Pancam images. According to an official press release the rover woke up at about 2:00 Mars local solar time to communicate with NASA's Mars Global Surveyor orbiter. At that time it took a few pictures of the night sky, in particular the Orion constellation. The picture on the press release says that the image had an exposure time of about 5 seconds. The raw images have an obviously longer exposure time because of the long star streaks. Anyway, what caught my attention was that on some of the images there seemed to have ‘stars’ with motion that was perpendicular to the rest of the stars. At first I thought that the streaks were meteors, but when comparing two images taken a few minutes apart, I noticed that one of the streaks had moved over a significant amount, but what would have been way too slow for a meteor. I’m including an animated gif of what I mean. The first frame was taken at 2:03:29 Mars local solar time and the second frame was taken at 2:08:36 Mars local solar time. I’ve drawn an arrow to the object I’m referring to. I think it’s either the Mars Global Surveyor or one of Mars’s moons (but I think that might not be likely given at what time the image was taken and how close of the orbits the moons have to the planet, but I could be wrong). Anyone else have an idea? If it is the Global Surveyor than I think these might be the first confirmed images of a man made satellite taken from the surface of another planet. Just wondering because I haven’t been able to find any information on it.
    Thanks!

    Here's the animated gif I made.

    https://www.physicsforums.com/attachment.php?s=&postid=164171
     
    Last edited: Mar 16, 2004
  2. jcsd
  3. Mar 16, 2004 #2
    UPDATE: the link doesnt work, I dont knwo why geocities is being stupid, but here's the animated gif I'm refering to.
     

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  4. Mar 16, 2004 #3

    enigma

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    Maybe Phobos or Deimos?
     
  5. Mar 16, 2004 #4

    Nereid

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    Perhaps this is what check is referring to?

    "Observing the sky with the green filter of it panoramic camera, the Mars Exploration Rover Spirit came across a surprise: a streak across the sky. The streak, seen in the middle of this mosaic of images taken by the navigation and panoramic cameras, was probably the brightest object in the sky at the time. Scientists theorize that the mystery line could be either a meteorite or one of seven out-of-commission spacecraft still orbiting Mars. Because the object appeared to move 4 degrees of an arc in 15 seconds it is probably not the Russian probes Mars 2, Mars 3, Mars 5, or Phobos 2; or the American probes Mariner 9 or Viking 1. That leaves Viking 2, which has a polar orbit that would fit with the north-south orientation of the streak. In addition, only Viking 1 and 2 were left in orbits that could produce motion as fast as that seen by Spirit. Said Mark Lemmon, a rover team member from Texas A&M University, Texas, "Is this the first image of a meteor on Mars, or an image of a spacecraft sent from another world during the dawn of our robotic space exploration program? We may never know, but we are still looking for clues.""
     
  6. Mar 16, 2004 #5
    https://www.physicsforums.com/attachment.php?s=&postid=164171

    No, that was something different. What you're referring to:
    [​IMG] & http://marsrovers.jpl.nasa.gov/gallery/all/spirit_p063.html was caught by the pancam on sol 63, The picture to which I'm referring https://www.physicsforums.com/attachment.php?s=&postid=164171 was taken on sol 67. It's possible its the same object though… I'm not sure of the specifics of the orbits of the satellites they got up there.
     
  7. Mar 16, 2004 #6

    Nereid

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    Got it now check.

    I think the first of the sol67 night-time piccies may have been 5 sec exposure; as you say, the other three seem much longer. Do you know how we could check? How we could estimate the likely exposure time?

    Regarding the moving object, "... some of the images there seemed to have ‘stars’ with motion that was perpendicular to the rest of the stars ... ", let's do some astronomy!

    We can identify the 'true stars' in the image (they're in Orion), and we can measure the position of the start and end positions of the 'perpendicular streaks' (we will get two positions for each, depending on whether we think the streak is moving right to left, or vice versa).

    From these four/eight (six/twelve?) positions, and knowing where Spirit is on Mars, what could we say about the streaks? Can we work out a rough orbit (assuming the streak is in orbit about Mars)?
     
  8. Mar 16, 2004 #7
    Well you could estimate the exposure times by looking at how long the streaks are. By knowing how far apart these known stars are spaced and by comparing that with the rotation time of Mars and the length of the streaks we could figure out how long the exposure was.
    Yeah, I knew that, just never bothered to do the math for it… but I think I might now.
    I guess also that if we knew how long the exposures were, or even by comparing the 2 pictures because we know what times they were taken at, we could determine how fast the 'object' was moving...if we knew its height above the planet that is. So I guess if we plugged in the known heights of the orbiting satellites and moons of Mars and see which one matched up with the velocity (at that altitude), we could, without figuring out the exact orbit of the observed object, match it up to other known objects.
    Does that make sense? Or is it too rambling? Sorry, I'm doing too much at once here.
    Anyway, thanks for the reply.
     
  9. Mar 17, 2004 #8

    Nereid

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    If we were doing a real experiment, there's one other thing I'd suggest we do before making lots of measurements on the rover images.

    You'll notice that most (all?) of the images have what seem like random points of light in them? Without knowing anything much about the 'cameras' (other than to guess they've got a CCD or two in their guts), I'd say these are cosmic ray hits (and some 'bad' pixels).

    As every amateur astronomer who's worked with CCD cameras knows, you need to do some processing before you can start treating the images as (semi-faithful) representations of light from the sky. In particular, you need to be clear about what sorts of artifacts can arise.

    Unfortunately, the list of possible artifacts is depressingly long.

    Fortunately, all (almost all?) artifacts behave in fairly understandable ways. For example, reflections - of a bright object off the 'tube' of the 'scope; 'dust' on the lens; faulty read-out electronics.

    For sure the folk who built the rovers have a pretty good idea of the kinds of artifacts that their cameras are likely to produce, and have a nice thick manual that they give to the scientists who will make use of the images for real science (it may be a 'manual in the mind', many scientists are the same people who developed the instruments!).
     
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