RELIKT-1 from Russian: РЕЛИКТ-1[a] (sometimes RELICT-1) was a Soviet cosmic microwave background anisotropy experiment launched on board the Prognoz 9 satellite on 1 July 1983.

A follow-up, RELIKT-2, would have been launched around 1993, and a RELIKT-3 was proposed, but neither took place due to the dissolution of the Soviet Union.

It used a superheterodyne, or Dicke-type modulation radiometer[2] with an automatic balancer for the two input levels with a 30-second time constant.

[3] The radiometer was calibrated to 5% accuracy before launch, as was an internal noise source (which was used every four days during observations).

[1] Additionally the moon was used as a calibrator, as it was observed twice a month,[3] and the in-flight system temperatures were measured to vary by 4% on a weekly basis.

[4] It observed for 6 months, giving 31 different scans that covered the whole sky, all of which intersected at the ecliptic poles.

The experiment ceased observations in February 1984,[1] after collecting 15 million measurements.

[2] It measured the CMB dipole, the Galactic plane,[2] and reported constraints on the quadrupole moment.

[1] The first dipole measurement was reported in 1984, while the telescope was still observing, at 2.1±0.5mK, and upper limits on the quadrupole of 0.2mK.

[3] It also detected brighter-than-expected Galactic plane emission from compact HII regions.

The results were close to those measured by the Cosmic Background Explorer[1] and the Tenerife Experiment.

[4] The launch was put back to 1996, with expanded plans to observe with 1.5-3° resolution from two spacecraft in 1995,[1] but ultimately never took place because of the Soviet Union's break-up and lack of funding.