Spread Spectrum In-Orbit Testing (IOT)

These new spread spectrum modems and associated techniques provide an ideal solution for performing frequency and amplitude response measurements of transponders in operation, without any interruption or degradation in the commercial services they carry. Spread spectrum is extremely useful in difficult frequency slot environments, where interference with neighboring satellites is an issue.

Besides frequency response applications, spread spectrum modems also open the door to a wide variety of other applications, including accurate and continuous satellite ranging measurements, frequency translation measurements and TWTA operation point determination. The systems also allow measurement of all of properties in a remote configuration in which the transmitter and receiver are located at different sites.

Spread spectrum techniques are particularly relevant for communication channel testing at beginning of life as well as regular verifications and emergency assessments. They present the ultimate solution for measuring signals with low spectral density and testing under load with no interference to payload or other channels.

Spread-spectrum techniques are applied daily on the ASTRA fleet for payload quality assessment, and are also extensively used in in-orbit testing campaigns.

Applications features:

Frequency response - amplitude and group delay
Low C/N (no interference)
Measurements on occupied transponder: live channels, i.e. with on-air payload signal, without degradation
Frequency translation
Translation frequency stability (long term, doppler compensated)
Monitoring of satellite receiver LO drift under load
TWTA operating point
Small signal suppression for determination of non-linear amplifier
Operating point (e.g. TWTA close to saturation)
Measurement without traffic interruption
Measurement of transfer curve drift (in FTS and D/L EIRP)
Intermodulation and cross-polarisation discrimination

The techniques carry an ASTRA patent.