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tony873004
2006-Feb-07, 11:45 PM
Does the Spitzer Space Telescope have engines to perform burns? Or is it incapable of adjusting its orbit?

Hamlet
2006-Feb-08, 01:44 AM
Does the Spitzer Space Telescope have engines to perform burns? Or is it incapable of adjusting its orbit?

I don't think so. The telescope uses reaction wheels for slewing to observing targets and nitrogen gas thrusters to perform reaction wheel momentum desaturation. I don't think Spitzer has a way to significantly alter its orbit.

ToSeek
2006-Feb-08, 03:25 AM
What Hamlet said - the thrusters are just cold gas, which is enough to take the load off the reaction wheels or to change the attitude of the spacecraft, not enough to change the orbit enough to matter.

tony873004
2006-Feb-08, 05:30 AM
Thanks Hamlet and ToSeek. I was pretty sure that was the answer, but I was simulating Spitzer's orbit.

It trails the Earth and distances itself by about 0.1 AU per year. In 2025 it will pass behind the Sun. I know it isn't designed to work this long, but the Mars rovers weren't designed to be going on their 3rd year either.

So I thought that maybe it carried some propulsion to correct for this. But a year later, it will emerge from behind the Sun and if it's still alive we'll gain communication again. In 2051 it will catch up to Earth again from the other side. Earth will seemingly repel it in the other direction. Spitzer is in a horseshoe orbit.

spfrss
2006-Feb-08, 07:57 AM
Thanks Hamlet and ToSeek. I was pretty sure that was the answer, but I was simulating Spitzer's orbit.

It trails the Earth and distances itself by about 0.1 AU per year. In 2025 it will pass behind the Sun. I know it isn't designed to work this long, but the Mars rovers weren't designed to be going on their 3rd year either.

So I thought that maybe it carried some propulsion to correct for this. But a year later, it will emerge from behind the Sun and if it's still alive we'll gain communication again. In 2051 it will catch up to Earth again from the other side. Earth will seemingly repel it in the other direction. Spitzer is in a horseshoe orbit.

Spitzer instruments (being it an IR telescope) are cooled by the slow evaporation of elium or hydrogen (I don't remember).
Spitzer is expected to run out of cooling gas in about five years from launch, maybe NASA with careful management will extend spitzer's useful lifetime by a few months, but absolutely not years.

Mauro

tony873004
2006-Feb-08, 08:20 AM
Spitzer instruments (being it an IR telescope) are cooled by the slow evaporation of elium or hydrogen (I don't remember).
Spitzer is expected to run out of cooling gas in about five years from launch, maybe NASA with careful management will extend spitzer's useful lifetime by a few months, but absolutely not years.

Mauro
Thanks for the info :). I think I read that they may extend it for a few years but I'm sure decades like I'm suggesting is out of the question for the reason you bring up.

So it will become a dead satellite in a solar horseshoe orbit sharing an orbit with Earth. I wonder if they will still be able to track it? One day it may re-enter Earth orbit as a UFO like the Apollo upper stage from a few years ago.

ngc3314
2006-Feb-08, 02:13 PM
Spitzer instruments (being it an IR telescope) are cooled by the slow evaporation of helium or hydrogen (I don't remember).
Spitzer is expected to run out of cooling gas in about five years from launch, maybe NASA with careful management will extend spitzer's useful lifetime by a few months, but absolutely not years.

Mauro

It does look as if purely passive cooling can keep the instruments cold enough for the short-wavelength camera (IRAC) to remain useful at least in its shortest two filter bands. From here (http://ssc.spitzer.caltech.edu/documents/ctfwhite/gowhite-tjj.htm): "we note that the short wavelength (InSb) instruments might operate for an indefinite period of time after the He cryogen has been exhausted, giving SIRTF limited long-lived capabilities". This is quite cool (like most of the stuff Spitzer looks at).

Saluki
2006-Feb-09, 02:48 PM
Has there been any consideration of a refueling mission, or would that cost more than sending up a new Spitzer?

ToSeek
2006-Feb-09, 04:03 PM
Has there been any consideration of a refueling mission, or would that cost more than sending up a new Spitzer?

Spitzer is in a solar orbit and would be very hard to get to (impossible for the shuttle).

Saluki
2006-Feb-09, 04:15 PM
I realized it was in solar orbit. I was thinking in terms of something unmanned. Probably still not feasible from a resourse standpoint.

ToSeek
2006-Feb-09, 04:18 PM
I realized it was in solar orbit. I was thinking in terms of something unmanned. Probably still not feasible from a resourse standpoint.

It probably wouldn't cost as much as Spitzer, but it would cost at least as much as your average robotic mission, i.e., you can have this but you'd have to cancel a Mars orbiter.