Item — HN Reader

> 2) SOFIA's wavelength coverage is different that JWST's or anything else that is in the pipeline.

Depending on what you mean by "pipeline", that isn't quite true. Work is being done on several far-inrared missions, such as SPICA[0]. I'd consider SPICA to be in "in the pipeline" and it will cover much (if not all) of the far-infrared that SOFIA does. So I wouldn't call JWST and SOFIA complementary; rather, SOFIA is a precursor observatory and a potential technology development platform (for things like SPICA; not so much for JWST, since the JWST instruments are already being built).

[0] https://en.wikipedia.org/wiki/SPICA_telescope

2 comments

Funding for SPICA is still far from certain, and if it happens, it will likely be toward the end of the SOFIA mission. I would agree, however, that it is appropriate to call SOFIA a precursor to SPICA.

I wonder how much more expensive Herschel would have been, if ESA had gone with an closed-cycle cooler instead of using a limited liquid Helium supply directly.

I'm not sure closed-cycle coolers can get as cold as evaporation of liquid helium? Herschel was cooled to ~1.7 K [0] while MIRI will only be cooled to 7K [1]. Also, with regard to reliability, evaporation of liquid helium is a pretty foolproof design, while closed-cycle systems can potentially break and end a mission early.

[0] https://en.wikipedia.org/wiki/Herschel_Space_Observatory#Ins...

[1] http://jwst.nasa.gov/miri.html

Are the individual instruments cooled to that temperature though? Because if they are not, then the difference doesn't matter.

Had a look at the SPIRE manual [0][1] and it seems that Herschel does include an Helium cooler to cool SPIRE and PACS to 300mK.

On the other hand a closed-cycle system can also extend the mission, since you won't run out of cooling at a fixed point in time.

[0] http://herschel.esac.esa.int/Docs/SPIRE/html/spire_handbook.... [1] http://herschel.esac.esa.int/Docs/Herschel/html/ch02.html