Space telescope and spacecraft update

NASA ended the Kepler spacecraft’s exoplanet-hunting mission, following an irreparable mechanical failure. http://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=292
This is exactly the same problem that initially crippled Hubble – gyroscope failure – you would have thought that they would have learnt enough in the intervening years to have fixed it. At least on Hubble since the last servicing mission it seems to have been fixed. Kepler was a planet-finder (transit) and astro-seismology telescope. Even I managed to find some new “planets” from Kepler data.

The NASA WISE telescope, that fantastic tool that found hundreds of thousands of new asteroids, as well as the third nearest star system https://en.wikipedia.org/wiki/List_of_nearest_stars and many other things, is going to be reactivated by NASA in September. http://www.jpl.nasa.gov/news/news.php?release=2013-257 It was de-activated when it ran out of hydrogen coolant. That means that it will no longer be able to see objects cooler than itself, so won’t be able to see any more Kuiper Belt objects for instance, but it will still bas able to see near-Earth objects and the greater timespan will allow their orbits to be tracked more accurately. The original cryogenics kept some sensors extremely cold, but the two sensors that were originally kept at a relatively balmy 32 Kelvin http://www.nasa.gov/mission_pages/WISE/spacecraft/index_prt.htm should still function. I hope that they can keep them colder than the external temperature of 190 Kelvin (-83 C). The Spitzer telescope has done great scientific work after its coolant ran out, so lets hope that the same is true of WISE.

The ESA Gaia telescope is due to be launched in November. This is a successor to the ESA’s Hipparcos mission. It is hoped that Gaia will be able to accurately map the position of a billion stars, about 1% of those in the Milky Way, giving us a 3-D map of the galaxy. https://en.wikipedia.org/wiki/Gaia_(spacecraft) It will give us the distance to brighter stars (down to magnitude 15) to an unprecedented 0.01 milli-arc-seconds, with is about 200 times as accurate as Hipparcos. Hipparcos had measured the distances to “only” 100,000 stars. The Gaia mission will last 5 years, with first results after 2 years and final results published in 2020. The completed satellite Gaia has already landed in French Guyana, where it will be launched. It will be placed in an orbit about the Lagrangian point L2 on the far side of the Moon (like other ESA satellites Herschel and Planck). Because it can only see in blue, visible and red bands, not infrared, it won’t be able to see any brown dwarfs. But it will be able to detect planets and brown dwarfs orbiting bright stars by the wobble in the motion of these stars. Gaia will also be used to see quasars and test general relativity. http://www.esa.int/Our_Activities/Space_Science/Gaia_overview

The ESA Rosetta spacecraft https://en.wikipedia.org/wiki/Rosetta_(spacecraft) is in deep sleep. It is still on track to visit comet 67P/Churyumov–Gerasimenko in mid 2014.

The NASA Dawn spacecraft is still on track to visit the Dwarf Planet Ceres in February 2015. https://en.wikipedia.org/wiki/Dawn_(spacecraft)

The NASA New Horizons spacecraft is still on track to flyby the Dwarf Planet Pluto (and its many moons) on 14 Jul 2015. https://en.wikipedia.org/wiki/New_Horizons

The NASA Juno spacecraft is still on track to start orbiting Jupiter in August 2016. https://en.wikipedia.org/wiki/Juno_(spacecraft)

The ESA Euclid spacecraft will be a follow-up to ESA’s Planck mission. It will be looking for dark matter, but in a completely different way to any previous space telescope. It’s going to look for the stretching and bending of images of distant galaxies due to the presence of dark matter between us and them. The launch is tentatively scheduled for 2020. https://en.wikipedia.org/wiki/Euclid_(spacecraft)

is there really no way to recycle coolant?

hydrogen is hard to contain. it leaks through most material. it basically just boils off and is lost to space.

Boris said:

hydrogen is hard to contain. it leaks through most material. it basically just boils off and is lost to space.

ok. someone will have to devise low draw magnetic containment or something :/

is hydrogen able to be contained in magnetic fields?

Boris said:

is hydrogen able to be contained in magnetic fields?

i inadvertently did not include electro in that sentence if that makes a difference

I think I read somewhere that Kepler also lost a third reaction wheel. Perhaps not.

It’d be interesting if it could still be used in “drift” mode, let the telescope point where it wants to and record whatever it sees. Very many telescopes (such as Arecibo) already operate like that. The field of view of Kepler is enormous, 12.1 degrees across, 115.6 square degrees in all, so a survey of the whole cosmos is quite possible. But I very much doubt is NASA will be doing that.

> is there really no way to recycle coolant?

The latent heat of evaporation is used to do the cooling. As hydrogen slowly evaporates into space it keeps the rest of the solid hydrogen cool. It’s simple, slow and keeps everything really cool.

A similar method of evaporative cooling using helium is used to keep MRIs cool.

Anything with recycling coolant would require pumps and radiators, which would increase the cost and weight of the mission.

However, there are also passive cooling mechanisms. Put a reflective, thermally insulating shield between heat sources (Sun, Earth, Moon) and the spacecraft, and have a radiator or natural radiation from surfaces on the cool side. A multilayer heat shield with four layers separated by vacuum ought to work well. That would cool the craft down until the radiation out equals that coming in from zodiacal light (sunlight scattered off dust grains), thermal radiation from interplanetary dust, stars, and the cosmic microwave background. The equilibrium temperature would then be well below 190 Kelvin but well above 2.7 Kelvin. The thermal radiation coming in from interplanetary dust would exceed other sources of input heat by a factor of almost ten. The orbit of WISE means that it can’t be shielded from radiation from the Earth and Moon.