A videometer is a European designed automatic docking system that guides an
Automated Transfer Vehicle
The Automated Transfer Vehicle, originally Ariane Transfer Vehicle or ATV, was an expendable automated cargo spacecraft, cargo spacecraft developed by the European Space Agency (ESA), used for space cargo transport in 2008–2015. The ATV desi ...
(ATV) towards the docking port of the Russian
Zvezda Service Module
''Zvezda'', also known as the ''Zvezda'' Service Module, is a module of the International Space Station (ISS). It was the third module launched to the station, and provided all of the station's life support systems, some of which are suppl ...
of the
International Space Station
The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...
(ISS).
[{{cite news, title=State of the art in automatic rendezvous, url=http://www.esa.int/esaMI/ATV/SEMZ2O57ESD_0.html, publisher=]European Space Agency
The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...
, date=2 April 2004 The ATV uses relative
global positioning system
The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide ge ...
(GPS) in order to close in on the ISS up to a distance of 249 m. Thereafter the ATV uses two videometers, together with additional data from
telegoniometer
A telegoniometer is a type of goniometer with remote control and readout. A goniometer is a device for varying the phase relationship(s) among two or more antennae in an array in order to steer its directionality without the need to physically mo ...
s, to automatically complete the docking maneuver. Both videometers are active during rendezvous with one acting as a back-up.
Retroreflectors located on the aft end of Zvezda module accurately reflect pulsed laser beams emitted by the videometer on the front of the ATV. The spot patterns of laser light returned from the passive reflectors are analysed by the image processors on the ATV to give its relative position and orientation to the ISS. The beam travel time to the videometer's 26 retroreflectors, contained in a 25mm cube, compute the distance between the two spacecraft and thus allowing it to identify, approach and mate to Zvezda's docking mechanism.
References
Components of the International Space Station