Spacecraft Design

The RadioAstron mission uses the satellite SPECTR (astrophysical module), which is under development by Lavochkin Association of Russian Aviation and Space Agency. This module will be used in several other scientific missions. The total mass of the scientific payload is about 2500 kg, of which the unfolding parabolic 10-m radio astronomy antenna's mass is about 1500 kg, and scientific package holding the receivers, power supply, synthesizers, control units, frequency standards and data transmission radio system - near 900 kg. The mass of the whole system (satellite and scientific payload) to be carried into orbit by the power "Zenit-2SB"-"Fregat-2CB" launcher is about 5000 kg. The total power supplied by the power system is 3.0 kW of which 900 W will be supplied for science payload.

There are following basic spacecraft subsystems:

• control radio complex including antennas,
• attitude control system,
• power supply system,
• thermal control system
• solar panel attitude control system,
• orbit correction engines,
• scientific date communication radio system with tracking antenna,
• overall onboard control system.

The spacecraft Control System has following major functions:

• finding the sun from arbitrary position, tracking and maintaining orientation toward the sun; the platform with the star tracker must be kept in the shadow,
• setup the base of three-axis orientation,
• orientation of the axes of the spacecraft in a given direction and stabilization relative to this direction with the accuracy of 30 angular seconds,
• controlling operation of the orbital correction engines,
• pointing the high gain antenna to the Earth tracking stations.

There are two kinds of movement execution devices: jet system and inertial devices. The inertial devices are the reaction wheels and the powered gyros. The reaction wheels will be used for spacecraft stabilisation in "fine" orientation mode. The powered gyros will be used for repointing of the spacecraft and for unloading of the reaction wheels. The jet system is a hydrazine thrusters system: it will be used during the creation of the base system of spacecraft orientation, for unloading of the powered gyros, and for orbit corrections.

The parameters of the spacecraft orientation are determined in an inertial reference frame. Depending on operating conditions and the instruments used in the control loop, they are not worse than those once indicated in the Table 1.

Table 1

• Basic Information
• Spacecraft Design
• Orbit
• Space Radio Telescope
• Multi-Frequency Synthesis in K-band
• Data and Phase Links
• Ground Support of the RadioAstron
• Observations
• Data Processing
• Status of the Mission
• Progress of the RadioAstron Project in Pictures