Chord lengths across main belt asteroids from stellar occultations in the near infrared

An asteroid occultation of a stellar source provides a direct measurement of the chord length across the asteroid with excellent precision. The method is independent of the brightness of the asteroid as well as its location anywhere in the solar system. At present stellar occultation predictions of main belt asteroids are available with sufficient precision to merit observations. At the 1.2 m telescope of Mt. Abu Observatory at Gurushikhar, a few well predicted main belt asteroidal occultations of stars mostly in the near IR J band (1.25 mu m) have been successfully carried out in the last few years. The NICMOS IR array camera was used in the fast subarray mode for this purpose. Details of the observations and results are discussed.