Global Transmission Services 2 (GTS-2) - 07.14.16
Global Transmission Services 2 (GTS-2) is a technology experiment for the test, validation and demonstration of radio transmission techniques for the synchronization of earth-based clocks and watches from the ISS. In addition the GTS data services, based on a unique coding scheme, could ultimately lead to commercial services, such as blocking of stolen cars or lost credit cards, directly from space. Science Results for Everyone
Let us synchronize our watches. This experiment tested synchronization of clocks on Earth and watches on the station using radio transmissions. An Ultra-Stable quartz clock with an accuracy of within one trillionth of a second provides unprecedented precision on station when synchronized with an atomic clock on Earth. Testing showed lower-than-expected signal strength, traced to interference from the hull of the module and blocking by the docking of the Soyuz spacecraft. Corrective measures for the signal strength were successful and ground hardware improvements allowed signal reception on every station pass. Second-generation testing ran from 2007 to 2009 and reactivation is expected in 2014. Experiment Details
Felix Huber, Ph.D., Steinbeis Transferzentrum Raumfahrt, Gaufelden, Germany
German Aerospace Center (DLR), Cologne, Germany
Sponsoring Space Agency
European Space Agency (ESA)
ISS Expedition Duration
April 2007 - October 2009
- The Global Transmission Services 2 (GTS-2) is designed to investigate the possibilities of transmitting a time signal from the International Space Station (ISS) to synchronize clocks on the ground.
- Time signal stations on Earth usually broadcast their information at long wavelengths. Watches and clocks synchronize themselves with these signals by activating their receivers typically once per day or after turn-on.
GTS is transmitting a UTC time signal from the Station via an external antenna with a broad antenna pattern. The Station's orbit means that this signal covers almost the whole globe every day. It can be received at any location several times daily, for 5-12 min at a time, strong enough for even small wrist watches. GTS also broadcasts the Station's current orbital position, so clocks know their local time zone.
GTS-2 will verify the performance and accuracy of a time signal broadcast to Earth from low orbit under real space operational conditions. GTS-2 will also measure the signal quality and data rates on the ground and measure disturbing effects such as Doppler shifts, multi-path reflections, shadowing and elevation effects.
GTS-2 is a continuation of the Global Transmission Services (GTS) experiment, which will be possible when a new electronic unit is launched on Progress flight 22P to the ISS. On 5 December 2005, the current GTS was re-activated, after a long time of theoretical investigations and practical tests to find out the reasons and successfully introduce corrective measures for the weaker than expected transmitted signal strength experienced by GTS receivers on the ground.
Operational Requirements and Protocols
Decadal Survey Recommendations
Information Pending^ back to top
The information provided is courtesy of the ESA Astrolab Mission web page.
NASA Image: ISS003E5477 - Cosmonaut Vladimir Dezhurov of Rosaviakosmos, Expedition Three flight engineer, holds a Global Time System (GTS) electronics unit in the Zvezda Service Module.
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