NASA’s Spitzer Space Telescope Ends 16-Year Mission | Hacker News Reader

NASA’s Spitzer Space Telescope Ends 16-Year Mission

nytimes.com

36 pointscyanbane8 comments

The telescope ran out of coolant in 2009, but it continued operating for quite a long time after that. The article says that one of the biggest concerns is the difficulty of communicating with it, as it falls further from Earth in its Earth-trailing orbit.

Compared to the 2.5-year mission specification, its lifetime was long. I know NASA over-engineers, and extends each mission as long as some hardware operates (see Opportunity), but that's still an impressive mission lifetime.

A nice article, but it would have been good to hear more about the specific justifications for shutting the telescope down in advance of JWST's launch. $14 million/year doesn't seem like that much, in the grand scheme of things.

Heck, why shut it down at all? Document the communication protocols and orbital elements, and turn it over to amateurs.[1]

We seem to have put an awful lot of our eggs in the JWST basket.

[1] https://uhf-satcom.com/dsn/dsnstart

From Caltech's Spitzer web pages:

Spitzer orbits the Sun on a path similar to Earth's but moves slightly slower. Today it trails about 158 million miles (254 million kilometers) behind our planet - more than 600 times the distance between Earth and the Moon. That distance, along with the curve of Spitzer's orbit, means that when the spacecraft points its fixed antenna at Earth to download data or receive commands, its solar panels tilt away from the Sun. During those periods, the spacecraft must rely on a combination of solar power and battery power to operate.

The angle at which the panels point away from the Sun has increased every year that the mission has been operating. These days, to communicate with Earth, Spitzer has to position its panels at a 53-degree angle away from the Sun (90 degrees would be fully facing away), even though the mission planners never intended for it to tilt more than 30 degrees from the Sun. Spitzer can communicate with Earth for about 2.5 hours before it has to turn its solar panels back toward the Sun to recharge its batteries. That communications window would grow shorter year after year if Spitzer continued operating, which means there is a limit to how long it would be possible to operate the spacecraft efficiently.

This was back in June 2019.

In addition, after it ran out of coolant back in 2009, they were able to only run one of its three instruments, and only two out of four wavelength channels on that.

Eventually they've reached a point where they cannot get enough science return for the costs of the personnel and DSN time.

TFA doesn't go into these details, but we might assume that if they can shut it off then they can also turn it back on. If that's the case, leaving it inactive may be the best thing to do in case a celestial event makes Spitzer's observations more valuable in future. If amateurs were controlling it, they might leave it in an unrecoverable state.

It ran out of coolant for its primary instruments, and the battery can only manage a short period each day for data transmission.

As the article says, they've already been working around that. It can no longer meet its rated performance specs, but it's far from useless.

The refrigerant was gone in 2009. It has still been useful, if decreasingly so, since then.

The its orbit in relation to Earth make it impossible for it to charge and send data to Earth. So while its not technically dead, its functionally unusable.

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