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Homework Help: Thermal Radiation of MARS problemo

  1. Feb 16, 2008 #1
    1. The problem statement, all variables and given/known data

    the thermal radiation of mars

    2. Relevant equations

    i understand earth radiates at 237W/m^2 into space but i cant find out how much mars radiates, i know it has an average temp of -55 degrees C so i know its going to be a lot less but i dont know how much. i need this for a spacecraft design project im doing

    3. The attempt at a solution

    see above

    would really apprieciate any help on this one guys

  2. jcsd
  3. Feb 16, 2008 #2


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    If you know the mean temperature you can make a pretty good guess using the Stefan-Boltzmann law.
  4. Feb 16, 2008 #3
    sure thing but as mars is not a blackbody then what value shall i use for the emmissitivty? (e in the equation P=e*sigma * t^4* area)

    also would atmospheric makeup have an effect?

  5. Feb 16, 2008 #4
    You can also calculate how much energy mars gets from the sun, mimus what it immediately reflects away (albedo). This avoids the error you make by taking the average temperature.
  6. Feb 16, 2008 #5
    sure thats sounds good,
    the albedo of mars is 0.15 so it will take in 0.85 of the suns energy after initial reflection.
    will it then re emit all of this?
    also does anyone know the relationship between altitude and thermal emmission, the satellite im trying to design will fly 278km above mars' surface so i'm trying to calculate the effect of mars on its temperature

    cheers all
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