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GRS1915+105 is an extraordinary X-ray transient which exhibits superluminal radio jets. In this paper, ASCA observations of the GRS1915+105 conducted from 1994 to 1997 are reported. Observations are carried out on the following dates each for ∼ 20 ksec exposure; Sep 27 1994, April 20 1995, Oct 23 1996 and Apr 25 1997.

One of the crucial steps in the occultation transform imaging technique involves the removal of the time-varying instrumental background. Previous versions of this imaging technique applied to BATSE data have used simple high-pass filtering to eliminate background variations on timescales longer than the typical duration of an occultation step (of order 10 s). We have investigated an alternative technique in which the imaging algorithm is applied to the residuals generated from fitting the raw data with a semi-empirical model of the background. Comparison of the resulting maps shows that the latter does not significantly improve imaging performance.

The large Area Detectors (LADs) of the BATSE experiment aboard the Compton Gamma-ray Observatory have been used recently as the first hard X-ray all-sky imager at energies between 20 keV and 300 keV. The Earth occultation process is formulated in terms of a curved Radon transform convoluted by a step transform in a selected field of view (FOV) ranging from 5° x5° to 40° x40°. The Maximum Entropy Method is then used to reconstruct an image in the hard X-ray sky. Multiple images of different regions of the sky can be produced simultaneously. A source location accuracy of 0.1° for strong sources and a sensitivity limit of 100 mCrab have been achieved in an one-day integration period.

Two-dimensional maps of the Crab Nebula have been synthesized in 22–64 keV range through the modulation collimator experiment. The effective angular resolution is about 15″. The result indicates that the Crab morphology is strictly controlled by the pulsar.