720 XTF Search Results (expand=subject;f1-spectral-Type=X-ray;f2-facility=1st High Energy Astronomy Observatory (HEAO-1);f3-type=Chart);f1-spectral-Type%3DX-ray;f2-facility%3D1st%20High%20Energy%20Astronomy%20Observatory%20(HEAO-1);f3-type%3DChart Results for your query: expand=subject;f1-spectral-Type=X-ray;f2-facility=1st High Energy Astronomy Observatory (HEAO-1);f3-type=Chart Thu, 01 Jan 1970 12:00:00 GMT HEAO-1 All-Sky X-ray Catalog. 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, carried NRL’s Large Area Sky Survey Experiment (LASS), consisting of 7 detectors. It surveyed the X-ray sky almost three times over the 0.2 keV - 10 MeV energy band and provided nearly constant monitoring of X-ray sources near the ecliptic poles. Thu, 01 Jan 1970 12:00:00 GMT