The following program is carried out in order to consolidate the PHT 
calibration of chopped measurements and derive signal losses due to the high 
chopper frequency compared to signal stabilization time.

- observation of alpha Boo (Arcturus, HR 5340): background and star
staring plus chopped measurements.
We intend to use well known calibration stars with a consolidated spectral
energy distribution. The star is sufficiently bright to be used as
a standard at wavelengths longward of 60 micron. Since the star is very
bright at the shorter wavelengths background observations are taken only
for filters longward of 60 micron.
 

Several filters are taken to have several contrast levels between background
and source. A second set of measurements is taken using shorter reset
interval, in order to increase the chopper frequency. To do this we have
to increase the fluxes to the double of its value.



.HISTORY
23/06/97        JA First version. Standard star is HR5340
26/08/97        JA Standard star is HR6705
18/09/97        JA Standard star is HR7341 for P1 detector
 
.OTT 7602 
.TDT 8042