Videometer
Encyclopedia
A videometer is a European designed automatic docking system that guides an Automated Transfer Vehicle
(ATV) towards the docking port of the Russian Zvezda Service Module of the International Space Station
(ISS). The ATV uses relative global positioning system
(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
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.
Automated Transfer Vehicle
The Automated Transfer Vehicle or ATV is an expendable, unmanned resupply spacecraft developed by the European Space Agency . ATVs are designed to supply the International Space Station with propellant, water, air, payload and experiments...
(ATV) towards the docking port of the Russian Zvezda Service Module of the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...
(ISS). The ATV uses relative global positioning system
Global Positioning System
The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...
(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
Telegoniometer
A Telegoniometer is a device for varying the phase relationship among two or more antennae, in an array for purposes of steering the directionality of the array, without physically moving the antennae...
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.