Integrated Star Tracker (IST)
The integrated star tracker has been designed for online determination of both orbit and s/c attitude control parameters. The Optico-physical department is conducting this development with the involvement of several cooperating enterprises. The IST design is based on the BOKZ family star trackers and the inbuilt receivers of navigation satellite signals and precise angular velocity sensors based on wave gyroscopy.
Algorithm of integrated star tracker operation:
- - the tracker's optical channel defines the parameters of s/c three-axis orientation by an image of the starry sky arbitrary section;
- - data received from the optical channel is used for gyro quasicontinuous calibration;
- - loss of the optical channel operation ability due to its field of view illumination by the Sun or large s/c angular velocity the attitude control parameters are determined by the inertial channel (gyro);
- - the prompt increasing optical channel operation ability is formed by inertial channel.
Integrated star tracker provides for solution of the following problems:
- - the UTC storage and clock signal grid generation;
- - navigation measurement filtering and orbit parameters calculation;
- - calculation of the s/c inertial orientation parameters;
- - calculation of the sidereal time current values and s/c attitude control parameters in the geocentric Greenwich coordinate system;
- - calculation of the s/c position at the ~10 Hz frequency as well as the vectors of the SC orbital velocity in the Greenwich coordinate system;
- - calculation of the s/c attitude control parameters in the orbital coordinate system; and
- - calculation with the frequency required of the external orientation parameters for the image data acquired by remote sensing systems.
The star trackers integration provides for improving the following s/c attitude control parameters: mass, dimensions, power consumption, measurement accuracy and noise immunity, cost reduction.