HEOS-1

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HEOS-1
HEOS-1
Type: Research satellite
Country: EuropeEurope Europe
Operator: ESRO
COSPAR-ID : 1968-109A
Mission dates
Dimensions: 105 kg
Size: 1.3 m diameter, 75 cm high
Begin: December 5, 1968, 18:55 UTC
Starting place: Cape Canaveral LC-17B
Launcher: Delta E-1
Status: burned up on October 28, 1975
Orbit data
Rotation time : 6690 min
Orbit inclination : 28.1 °
Apogee height :  227099 km
Perigee height :  6804 km
Eccentricity : 0.893

HEOS-1 ( Highly Eccentric Orbit Satellite , English for: satellite with a strongly eccentric orbit) was a satellite of the European research organization ESRO . In the early stages, the satellite was also known as HEOS-A .

task

The HEOS-1 satellite was designed to accommodate a number of experiments aimed at studying the magnetic field and the energy distribution of protons and electrons in a period of expected high solar activity .

The satellite was designed to last for one year. The main contractor for the satellite was Junkers Flugzeug- und Motorenwerke from Germany. Lockheed Aircraft Germany acted as a consultant . Other contractors were BAC from Great Britain ( position control ), ETCA from Belgium (electrical systems) and Snecma from France (temperature control).

construction

Basic structure

The basic structure of the satellite was a cylinder about 130 cm in diameter and 70 cm in height. It had an axial boom on the top so that the magnetic field sensors and antennas could be attached at a certain distance. The surface was a 16-sided polyhedron and up to 70% was covered with solar cells . An equatorial zone near the center of gravity, 70 mm wide, was reserved for the installation of the experiment and flight attitude sensors. The remaining free cylinder surfaces were covered with a heat protection layer. The top and bottom of the satellite were equipped with removable panels, which reinforce the satellite cell and provide additional surfaces for temperature control. The primary cell consisted of the satellite adapter, the octagonal center tube and four brackets that carried the solar cell panels, which in turn represented the outer surface. The three-legged boom was attached to the upper part of the octagonal tube on three supports. This adaptable configuration was able to accommodate a variety of different experiments with only a few changes to be made.

Magnetic design

Due to the nature of the experiments, great emphasis was placed on the magnetic purity of the entire satellite. Magnesium , aluminum and titanium were the main materials of the basic structure. The utmost care has been taken in manufacturing and handling to avoid magnetic contamination. Electrical circuits and wiring harnesses were designed so that stray magnetic fields could not occur. All components have been selected with the aim of keeping the use of magnetic materials to a minimum. In addition, extensive tests were carried out to determine and reduce permanent and stray magnetic fields.

Position control

HEOS-A received a spin stabilization that made it possible to orient the spin axis in relation to the plane of the ecliptic either parallel, perpendicular or in any intermediate position and approximately perpendicular to the direction of the sun. The position stabilization was achieved by using the gyroscopic effect. The missile was allowed to rotate about its longitudinal axis at a nominal rotational speed of 10 revolutions / min. The top speed system was controlled from the ground. The satellite spin was increased or decreased by a cold gas system , the two gas nozzles of which were arranged at the "equator" of the satellite. The realignment of the spin axis was either controlled from the ground or it took place via an on-board closed control loop in the satellite. The reorientation of the spin axis took place via a pulse-controlled, precession- generating cold gas nozzle on the bottom edge of the satellite.

Power supply

8576 photoelectrically working solar cells made of silicon and a magnetically pure silver-cadmium battery of 5 Ah delivered 42 W for all experiments, telemetry , charge control and the measurement subsystems. The power supply system also ensured that all consumers received their voltage regulated as required . The electricity was distributed via a distribution box. During the shadow period that occurs near the perigee , the battery was used.

Temperature control

A passive system was used to maintain the temperatures within the permissible limits during start preparations, the ascent phase and during operation. During normal operation, the temperatures were as close as possible to the optimum value. Three conditions in orbit were considered: (A) full solar radiation: the satellite spent most of its operational life in sunlight; (B) short eclipse: it lasted a maximum of 45 minutes. During this time, all experiments and subsystems remained in operation; (C) long eclipse: up to 4.5 hours; During this time, all devices with the exception of the receiver for receiving commands and its power supply were switched off.

Telemetry

An integrated transponder device weighing 5.5 kg and having an output of 20 watts was used simultaneously for telemetry, remote control and path tracking. The system received digital data on 63 channels and analog data on 64 channels, which were assigned one after the other. In accordance with the ESRO ground stations , a transmission frequency of 136 to 138 MHz was chosen. The omnidirectional antenna was designed in such a way that, with a transmission power of 5.5 watts, it enabled perfect reception from satellites for every flight position up to an apogee of 300,000 km. A standard sound subsystem was used for the transmission of commands, with which up to 70 different commands were transmitted on the frequency of 145.25 MHz.

Experiments

The experiments on board the satellite had a total weight of 25 kg and an electrical power requirement of 7.5 W. The following experiments were involved:

Orbit

The orbital parameters of the highly elliptical orbit were chosen so that the satellite would not enter the earth's atmosphere for at least a year despite the gravitational disturbances from the moon and sun. The proximity to the earth lay over the northern hemisphere , the distance from the earth over the southern hemisphere. From the start, the proximity to the earth remained at most 90 days in a half-space that is bounded by the plane that is perpendicular to the direction of the sun and that contains the center of the earth. This ensured that the satellite would be outside the Earth's bow shock wave for at least 24 hours per orbit for the first three months . Favorable starting windows appeared in late 1968 and early 1969.

Cooperation with NASA

Since ESRO did not have a European launcher with the necessary performance, the launch was carried out by the US American NASA . ESRO was the first foreign organization to pay NASA for a launcher and launch, and HEOS-1 was the first satellite to be launched under this framework.

Mission history

HEOS-1 was launched on December 5, 1968 from Cape Canaveral in the USA. A Delta E-1 served as the launch vehicle . The operation of the satellite was completely satisfactory for 16 months, after which the first defects appeared. From 1975 on, only the magnetic field experiment was still operational and telemetry only worked 50%. On October 28, 1975, the satellite re-entered the earth's atmosphere . The successor HEOS-2 was launched on January 31, 1972.

Individual evidence

  1. ↑ HEOS-1 in the NSSDCA Master Catalog , accessed April 7, 2019.
  2. ↑ ESA: HEOS. Archived from the original on October 14, 2006 ; accessed on July 5, 2019 .
  3. ↑ NASA: Satellites. In: Origins of NASA Names. 1976, p. 46 , accessed on September 9, 2010 (English): “Under a December 30, 1966 memorandum of understanding, ESRO became the first international space group to agree to pay NASA for launchings; it would reimburse NASA for launch vehicle and direct costs of equipment and services. The first satellite orbited under this agreement, HEOS I- "Highly Eccentric Orbit Satellite" -was launched 5 December 1968. "

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