Beginning in 1977, NASA launched a series of
very large scientific payloads called High Energy Astronomy
Observatories(HEAO). The first of these missions, HEAO-1 surveyed the
X-ray sky almost three times over the 0.2 keV - 10 MeV energy band,
provided nearly constant monitoring of X-ray sources near the ecliptic poles.
More detailed studies of a number of objects were made through pointed
observations lasting typically 3-6 hours.
Mission Characteristics
Lifetime : 12
August 1977 - 9 January 1979 Energy Range :
0.2 keV - 10 MeV Payload :
A1 - Large Area Sky Survey experiment (LASS) :
0.25-25 keV, eff. area 7 modules each of 1350 - 1900 cm2,
FOV varied between 1° X 4° to 1° x 0.5° for finest collimators.
A2 - Cosmic X-ray Experiment (CXE) :
six separate proportional counters
Low Energy Detectors (LED) 0.15-3.0 keV, eff. area 2 detectors
of 400 cm2 each
Medium Energy Detector (MED) 1.5-20 keV, eff. area 1 detector at
800 cm2
High Energy Detector (HED) 2.5-60 keV, eff. area 3 detectors at
800 cm2 each
MED and HEDs had various FOV settings, 1.5° x 3°, 3° x
3° and 3° x 6°
Lifetime : 12
August 1977 - 9 January 1979 
