BLITS

BLITS (Ball Lens In The Space) is a Russian satellite launched on September 17, 2009, as a secondary payload on a <a href="/facts/Soyuz-2_(rocket)/U3nHlUKx">Soyuz-2.1b/Fregat</a>, from the <a href="/facts/Baikonur_Cosmodrome/sk16LwcH">Baikonur Cosmodrome</a> in Kazakhstan.
The satellite is totally <a href="/facts/Passive_satellite/9HbLomqw">passive</a> and spherical, and is tracked using <a href="/facts/Satellite_laser_ranging/y5GjpCNF">satellite laser ranging</a> (SLR) by the <a href="/facts/International_Laser_Ranging_Service/y5GjpCNF">International Laser Ranging Service</a>. The design of BLITS is based on the optical <a href="/facts/Luneburg_lens/LhBs8ky8">Luneburg lens</a> concept. The retroreflector is a multilayer glass sphere; it provides uniform reflection characteristics when viewed within a very wide range of angles, and can provide a cross-section sufficient for observations at low to medium orbit heights. A similar design was already tested on a smaller laser reflector carried on board of the <a href="/facts/Meteor_(satellite)/YkA5oFWR">METEOR-3M</a> spacecraft launched on December 10, 2001.
The purpose of the mission was to validate the spherical glass retroreflector satellite concept and obtain SLR (<a href="/facts/Satellite_laser_ranging/y5GjpCNF">Satellite Laser Ranging</a>) data for solution of scientific problems in geophysics, geodynamics, and relativity. The BLITS allows millimeter and submillimeter accuracy SLR measurements, as its "target error" (uncertainty of reflection center relative to its center of mass) is less than 0.1 mm. An additional advantage is that the Earth's magnetic field does not affect the satellite orbit and spin parameters, unlike retroreflectors incorporated into active satellites. The BLITS allows the most accurate measurements of any SLR satellites, with the same accuracy level as a ground target.
The satellite was inserted into an 832 km (517 mi) <a href="/facts/Sun-synchronous_orbit/3HonupUd">Sun-synchronous orbit</a>, with an inclination of 98.85º. The satellite was spinning at a spin period of 5.6 seconds around the axis normal to its orbit plane, allowing <a href="/facts/Laser/jk6PTvvT">laser</a> light to be reflected in short bursts because only half of the satellite is covered in a reflective coating. As the satellite is made of glass, minimal in-flight spin slowdown was expected since there were no conducting parts where currents interacting with the Earth magnetic field can be induced.
The expected operative life was at least five years, but the mission was interrupted in 2013 after a collision with <a href="/facts/Space_debris/X7YSKlXl">space debris</a>.

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BLITS