Contract activities on ISS Russian Segment

Experiment GTS


The first contract research activity to be performed on the ISS Russian Segment is ESA-provided Global Time System experiment.
Currently it became necessary to receive high-precision time signals by various users, i.e. Institutes of Nuclear Physics.
A possibility of precise time signals downlink from a low-orbit vehicle several times per day is first provided. In so doing, virtually all densely populated areas of the Earth are covered. Thanks to the original software and signal modulation it is possible to receive time codes depending on the time zone.
The experiment tests time signal and data signal receiving conditions on the ground by dedicated receivers. The time signal will have a dedicated code which enables the receiver to determine a local time in any location on the Earth with no user involvement.

Objective:

Reception of a downlinked high-accuracy time signal.

Tasks:

  • Installation of electronics unit and connection of the GTS equipment to the ISS service systems, performance of test activation of the GTS electronics unit and transmitters, as well as long-duration (for 658 days) activation of the GTS equipment with a 400 MHz transmitter.
  • Testing of time signal generation conditions using special ground receivers.
  • Checking the quality of the signal generated on the ground and data transfer rates.
  • Measuring disturbing effects of Doppler shift, retroreflections, shading and angle of elevation on the time signal.

Science Hardware Used:



GTS equipment:

  • Transmitters of 400 MHz, 1.5GHz band
  • Receiver of 450 MHz band
  • Antenna unit with attachment mechanism
    for downlink of high-accuracy time signals
  • HF cables

Flight Equipment Used:

  • Line multiplexer system unit
  • TV exchange module

Expected Results:

Testing the characteristics and accuracy of a time signal transmitted from a low-altitude near-earth orbit to the ground in real space conditions.