During 1987-88 (for two years), I was on leave from TIFR, Mumbai to work at California Space Institute, UCSD, USA on "Gamma Ray Spectrometer experiment" (GRS) aboard NASA's Mars Observer mission. I worked with Prof. J. R. Arnold who was member of the investigator team of GRS. The GRS experiment used 140 cc high resolution high purity Germanium detector to provide gamma ray measurements in 0.2 to 10 MeV energy region with high energy resolution (at 1.33 MeV FWHM <=2.0 KeV).  Mars  Observer  was launched successfully on Sept. 25, 1992 from Cape Canveral.  The   sapcecraft cruised  well right upto Mars during its  nine months journey, but  lost contact just as its arrival  on  Aug. 21, 1993,  When it was to ignite its thrusters to enter Mars orbit.  Its  fate is  unknown.

My contributions to GRS included three different tasks :

1. Background interference reduction
2. Data analysis procedure for GRS, and
3. Radiation damage to GRS detector and its annealing in space.

1. Weak peak problem in high energy gamma ray spectroscopy

Yadav J S, J Bruckner and  J R Arnold
Nuclear Instruments and Methods, A 277, 591, 1989
 
2. Radioactive material screening for gamma ray spectrometer experiment on Mars

Yadav J S and J R Arnold
Nuclear Instruments and Methods, A 295, 241, 1990