# Astronomical Netherlands Satellite

General information The flight spare for the satellite NISR / NASA[1] 30 August 1974[1] SLC-5, Vandenberg AFB, USA[2] 20 months[1] 266 to 1176 km[2] 99.2 min[2] X-ray and ultraviolet 1.5 to 30 KeV[3] 5 channels, 150 to 330 nm[4] References: [1][2][3][4]

The Astronomical Netherlands Satellite (ANS; also known as Astronomische Nederlandse Satelliet) was a space-based X-ray and ultraviolet telescope. It was launched into Earth orbit on 30 August 1974 at 14:07:39 UTC in a Scout rocket from Vandenberg Air Force Base, United States. The mission ran for 20 months until June 1976, and was jointly funded by the Netherlands Institute for Space Research and NASA.[1][2] ANS was the first Dutch satellite, and the Main Belt asteroid 9996 ANS was named after it.[5]

The telescope had an initial orbit of with a periapsis of 266 kilometres (165 mi), an apoapsis of 1,176 kilometres (731 mi), with inclination 98.0° and eccentricity 0.064048, giving it a period of 99.2 minutes.[2] The orbit was sun-synchronous, and the altitude of the spacecraft could be controlled via magnetic coils that interacted with the Earth's magnetic field, as well as by reaction wheels. The satellite also had two masses that were ejected early in the mission, which removed most of the satellite's angular momentum. The altitude could be measured by a variety of techniques, including solar sensors, horizon sensors, star sensors and a magnetometer.[1]

ANS could measure X-ray photons in the energy range 2 to 30 KeV, with a 60 cm$^2$ detector, and was used to find the positions of galactic and extragalactic X-ray sources. It also measured their spectra, and looked at their variations over time.[1] It discovered X-ray bursts, and also detected X-rays from Capella.[5]

ANS also observed in the ultraviolet part of the spectrum, with a 22 cm (260 cm$^2$) Cassegrain telescope. The wavelengths of the observe photons were between 150 and 330 nm, with the detector split into five channels with central wavelengths of 155, 180, 220, 250 and 330 nm.[4] At these frequencies it took over 18,000 measurements of around 400 objects.[1]