Goddard High Resolution Spectrograph
The Goddard High Resolution Spectrograph (GHRS or HRS) was a spectrograph installed on the Hubble Space Telescope. It was replaced by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) in 1997. The instrument is named after 20th century rocket pioneer Robert H. Goddard.
One of the results was the discovery of tenuous atmosphere for Jupiter's moon Europa in 1995. The gas was determined to be mostly of molecular oxygen (O2). The surface pressure of Europa's atmosphere is 0.1 μPa, or 10−12 times that of the Earth.
A technical description of the construction and operation of the GHRS can be found in NASA technical report CP-2244.
...
Wikipedia