The Astronomical Netherlands Satellite or ANS, also known as Astronomische Nederlandse Satelliet, the first Dutch artificial satellite, was a space-based X-ray and ultraviolet telescope. Launched into a high inclination, Sun-synchronous orbit, it was designed as an astronomical observatory. The spacecraft was attitude-controlled by magnetic coils interacting with the Earth’s magnetic field. Due to a first-stage guidance failure, the desired five hundred kilometres circular orbit was not obtained. Instead, the satellite was placed in an elliptical orbit that caused initial problems with the background radiation and complicated the scheduling of the observations. The satellite contacted the ground station once every twelve hours. The observing time was divided equally between the experiments on a one-orbit-per experiment basis.
The satellite, notable for its discovery of X-ray bursts and of the first X-rays from the corona of a star beyond the Sun (Capella), was launched from the Vandenberg Air Force Base (a United States Air Force Base in California) on August 30, 1974 in a Scout rocket (an acronym for Solid Controlled Orbital Utility Test system): the Scout family of rockets were American launch vehicles designed to place small satellites into orbit around the Earth. The Scout multistage rocket was the first (and for a long time, the only) orbital launch vehicle to be entirely composed of solid fuel stages. The original Scout was designed in 1957 at the Langley Research Center. Scout launch vehicles were used from 1961 until 1994.
Astronomical Netherlands Satellite, the first Dutch satellite
In June 1655 Christiaan Huygens, the great Dutch mathematician, astronomer and physician, sent an anagram to John Wallis in London consisting of a verse of Ovid. The verse was “Admovere oculis distantia sidera nostris”, meaning “distant stars move towards our eyes”. With this anagram, Huygens claimed his discovery of Titan, the largest moon in our Solar system. As a seafaring nation the Republic of the Netherlands showed great interest in the movement of celestial bodies, mainly for position determination; this formed the basis of the long-standing tradition of astronomical research in the Netherlands of which Huygens was a shining example.
By the mid-1960s, it was becoming clear that the Netherlands commercial sector was not very successful in obtaining orders for European space projects, at least not the orders that were technologically challenging. Under the ESRO/ELDO agreements, the contribution of each country to the budget of the European organisation determined the value of the contracts awarded to this country, so the money spent came back anyway. The problem was that it did not do very much for the building of technical and operational capacity.
The obvious solution was for the Netherlands to build its own satellite, thus showing to the world that the country had the technical and managerial capacity needed for space exploration. A working group, spontaneously formed by representatives from Fokker, Van der Heem Electronics and Philips, submitted a proposal to develop such a satellite in 1966: the Netherlands Astronomy Satellite.
The Astronomical Netherlands Satellite, a collaborative mission between the Netherlands and USA, ran for twenty months until June 1976, and was jointly funded by the Netherlands Institute for Space Research (the Dutch expertise institute for space research: the Institute develops and uses innovative technology for research in outer space, focusing on astrophysical research, Earth science and planetary research) and NASA. The telescope had a periapsis of two hundred and sixty-six kilometres, an apoapsis of one thousand and one hundred and seventy-six kilometres, giving it a period of almost one hundred minutes. The orbit was Sun-synchronous, and the attitude of the spacecraft could be controlled through reaction wheels.
A Sun-synchronous orbit, also called a heliosynchronous orbit, is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet’s surface at the same local mean solar time. More technically, it is an orbit arranged so that it precesses (precession is a change in the orientation of the rotational axis of a rotating body) through one complete revolution each year, so it always maintains the same relationship with the Sun.
The momentum stored in the reaction wheels throughout the orbit was regularly dumped via magnetic coils that interacted with the Earth’s magnetic field. The satellite also had two masses that were released shortly after orbit injection, to remove most of the satellite’s angular momentum induced by the launcher. The attitude could be measured by a variety of techniques, including solar sensors, horizon sensors, star sensors and a magnetometer.
The University of Groningen and Utrecht University, in Netherlands, provided some experiments, while the American Science and Engineering company, an American manufacturer of advanced X-ray equipment and related technologies, originating in 1958 as a developer for NASA, with an early focus on X-ray astronomy, provided the hard X-ray experiment.
The Dutch spacecraft was a three-axis stabilized, with one axis always pointed to the Sun, and the experiments were mounted perpendicular to the Sun line. The Astronomical Netherlands Satellite, with a mass of almost one hundred and thirty kilograms, could measure X-ray photons in the energy range two to thirty keV, with a sixty centimetre square 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.
Experiments on board observed celestial objects in UV and X-ray wavelengths. During its observing lifetime of twenty months (September 1974 to June 1976), ANS measured the positions, spectra, and time variations of galactic and extragalactic X-ray sources. A duplicate ANS satellite was built as a back-up, but was not launched. It was later donated to a museum.
Almost three years later, in July 1977, ANS returned into the Earth’s atmosphere. It was kept in operation between September 1974 and December 1975 and turned on again shortly in March and April 1976. ANS is still considered a great success. First of all because of the scientific results that were obtained. Both the X-ray and ultraviolet measurements have produced a lot of data, amounting to years of work. Three new types of X-ray sources were identified and the ultraviolet spectrometer proved the existence of very hot stars in our galaxy.
Apart from the scientific results ANS also demonstrated the technological capability of the Netherlands. Although the different systems on board were designed for a six months lifetime they lasted for nearly three years. The attitude control worked better than expected.
The scientific, technological and operational success of the ANS-mission established the Netherlands as a space-faring nation. Add to that the fact that, compared with other space projects, the ANS was carried out on a shoestring then it is no wonder that it invited some technologically challenging orders from ESA, NASA and others for years to come, not only for advanced instrumentation but also for solar arrays, robotics and attitude control systems. An evaluation study revealed that ANS had fulfilled its expectations with respect to its scientific and technological goals and the increased competitiveness of Dutch industry.