On April 30th 1996 BeppoSAX was successfully launched from Cape Canaveral.
Following launch the satellite was commissioned for two months. On June 22
1996 the HPGSPC made its first observation of a celestial X-ray source the
black-hole candidate 
. At the time of writing the HPGSPC is
completing the Science Verification Phase observing a number of well known
X-ray source.
Figure 26: Background count rate
observed by the HPGSPC during in flight operation. Three consecutive
orbits are shown. The upper curve refers to the count rate measured at
the
trigger while the bottom curve shows the residual background after
on-board burst length selection
Characterisation of background is one of the main goal of the Science
Verification Phase. Very preliminary results show that while the
count-rate at the Trigger level is about a 
counts/sec after
on-board burst length selection the background is reduced to 
counts/sec. Moreover, as can be seen in Fig. 26 (click here) the background
is clearly modulated with the orbit. If the FG technique is applied the
background count rate is reduced to 
counts/sec in the
40-60 keV band, that means a flux of 
that confirms what
expected on the basis of the on-ground calibration. Unfortunately the
background spectrum, reported in Fig. 27 (click here), is highly structured.
This is essentially due to a imperfect subtraction of the photons coming
from the calibration sources. We are currently working to optimally
configure the instrument in order to reduce this effect. A complete
in-flight characterisation of the instrument and its performances will be
subject of a future paper.
Figure 27: Background spectrum as observed by the HPGSPC during the
Commissioning Phase. The 
line is due to events from
calibration sources not well subtracted. Pb fluorescences are due to
the 88 keV component of the 
calibration source