Viking, the first Swedish satellite

Viking, the first Swedish satellite, was launched on an Ariane 1 rocket as a piggyback payload together with the French satellite SPOT 1, on February 22, 1986. Operations ended on May 12, 1987. Viking was used to explore plasma processes in the magnetosphere and the ionosphere.

The Ariane 1 rocket was a three stage liquid fuel rocket with a lift-off mass of two hundred and thirty-five tons. The rocket was fifty meters long and had a diameter of approximately three and a half meters. The third stage used liquid oxygen and liquid hydrogen. After the launch from Kourou on February 22, 1986, Viking was put into an eight hundred and twenty-two kilometres circular parking orbit. This orbit was raised to reach scientifically interesting regions.

The Viking project was managed by the Swedish Space Corporation (SSC) under contract from the Swedish Board for Space Activities, the Swedish government’s space agency. SSC is a government-owned organisation responsible for the execution of Sweden’s space program. The satellite was developed by SAAB Space with Boeing Aerospace as a major subcontractor.

Viking’s perigee boost motor placed this relatively small satellite (two hundred and eighty six kilograms) into a final eight hundred and seventeen / thirteen thousand five hundred and thirty kilometres polar orbit, where it conducted scientific observations of complex plasma processes in the magnetosphere and ionosphere of the Earth. The satellite carried experiments to measure electric fields, magnetic fields, charged particles, waves, and auroral images. These experiments were supplied by scientific teams from Sweden, Canada, Denmark, France, Norway, the United States of America, and the Federal Republic of Germany.

Viking, the first Swedish satellite

In the spacecraft, space was limited underneath the SPOT 1 satellite, and Viking had to be quite sturdy in order to withstand the stress of launch. The basic shape of the Swedish satellite was a flat octagonal disc, fifty centimetres thick and almost two metres across. The mechanical interface of the payload adapter from the Ariane rocket was duplicated on top of Viking. This enabled it to be added to the launch with a minimum of redesign of the SPOT 1 satellite. After SPOT 1 had been released, Viking fired its own rocket engine and was sent into its proper polar orbit.

A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It therefore has an inclination of (or very close to) ninety degrees to the body’s equator. A satellite in a polar orbit will pass over the equator at a different longitude on each of its orbits. The satellite conducted a very successful magnetospheric research mission until May 12, 1987.

After the scientific mission ended, both Viking and the upper stage of the rocket used to launch the satellite became derelict objects that would continue to orbit Earth for many years; both objects remain in orbit.

Viking, the first Swedish satellite, was operated by a crew of four people from a control room at the “radar hill” at Esrange. During the design life of eight months mission operations were nominal, but in October 1986, a short occurred in one of the electrical shunts used to dump excess solar panel power. On May 12, 1987, it was not possible to keep the battery charged any longer and contact was lost with Viking, the first Swedish satellite.

History of Viking, the first Swedish satellite

In recognition of the growing market for satellite services and the desirability of promoting Swedish industry’s capabilities in this field the Swedish space budget was increased considerably in the early 1980s. Given Sweden’s long traditions in magnetospheric and ionospheric research it was only natural that the first national satellite should carry an advanced magnetospheric research payload into regions of space believed to hold many secrets of this scientific discipline. Thus Viking’s mission was twofold: to be an industrial policy tool helping Swedish industry expand its capabilities in the space technology area, and to perform a qualified “scientific first” space exploration. A similar such project was discussed in 1970. An ambitious study of the project, called “The Swedish Satellite”, to be launched by a Scout rocket was performed by SAAB. However, lack of political support prevented the initiation of that project.

The Viking project was started in January 1978 with discussions with the Interkosmos council of the Academy of Sciences of the Soviet Union about a joint magnetospheric satellite project, named M-SAT. In March 1978, a preliminary technical proposal was submitted to the Interkosmos council. In November 1978, first contacts were taken with Boeing Aerospace about using their technology from the S-3 (Small Secondary Satellite, a series of scientific satellites launched piggyback on classified payloads) program and the Applications Explorer Missions.

In 1979, a feasibility study of M-SAT was conducted by SAAB and Boeing, and SSC first considered the use of an Ariane piggyback launch. In September 1979, the use of a Soviet rocket was abandoned, and Ariane 1 was chosen as the launch vehicle. A project definition study was run until June 1980 and on August 21, 1980, the Swedish Cabinet approved the project. The development contract with SAAB was signed on September 1, 1980.

The preliminary Design Review was held in March 1981 and the Critical Design Review in October 1981. The satellite platform was delivered by Boeing to SAAB in December 1982. The solar simulation test at ESTEC was conducted in July 1983. Because of delays in the launch of the main satellite SPOT (originally foreseen to occur in March 1984), Viking, the first Swedish satellite, was put “in mothballs” in November 1983.

In the fall of 1984, some tests (including the magnetic cleanliness test) were performed. In March 1985, joint vibration tests with SPOT were conducted in Toulouse. Viking was shipped to Toulouse for launch in September 1985, but the launch was delayed again because of the failure of Ariane V15. Viking, the first Swedish satellite, arrived in Kourou in October 1985, and staff from SSC arrived at the launch site on November 11, 1985.

The Viking Ground Station

The Viking Ground Station was located at Esrange, close to the northern border of Sweden. Since the spacecraft carries no tape recorder, observations were acquired only when it was in view of the tracking station. Measurements were made continuously from the time when Viking comes close to the auroral field lines (when it is above the polar region) until the time when it left the auroral field lines on the other side of the pole.

Telemetry data from Viking, the first Swedish satellite, were received and processed on a real time basis at the Esrange tracking station located near Kiruna, Sweden, above the Arctic Circle. These data were reduced and displayed by computer graphics techniques immediately after reception at the ground station. Scientists engaged in collaborative analysis of the space plasma phenomena at nearly the instant they are observed. Special “campaigns” were conducted that focus on special scientific topics and coordinated observations were made with surface, balloon, rocket and other satellite programs.

The Viking program is unique because experiment modes could be changed on a nearly real-time basis in order to concentrate on special phenomena that may be occurring at the moment. Another unique feature of this program is the data distribution system to the international community of scientists. A series of Quick Look Plots (QLP) were produced and distributed on a weekly basis to any scientist in the world for a small charge. These plots contain summaries of the information acquired by all Viking instruments. The goal was to inspire interest in the Viking data from the international scientific community.

Scientific Objectives

Northern Scandinavia is among the most favourable places on Earth to measure phenomena related to the coupling of energy between the Sun and outer space with the lower atmosphere and ionosphere. This is because the auroral zones are the focal points for this energy deposition, which can reach one thousand and eleven watts. The most spectacular manifestation of this phenomena is the northern lights or aurora, which have been studied for centuries by Scandinavian scientists.

The auroral regions encompass a dynamic and complex system of plasmas that interact with magnetic fields and electric currents. The Viking program was directed at understanding large-scale phenomena, such as plasma convection, global current systems, and auroral morphology, as well as small scale and microphysical problems, including particle acceleration processes, wave-particle interactions, shock structure, fine-structured currents, and Auroral Kilometric Radiation (AKR). Viking was specifically designed to perform high resolution measurements of electric fields, magnetic fields, energetic particles, plasma waves, and ultraviolet emissions. The orbit was chosen to sample the auroral plasmas at intermediate altitudes that are not usually explored by satellites and where a wealth of interesting processes is predicted to occur, including the key mechanisms responsible for the acceleration of auroral particles.