It was essentially a copy of the DOS 3 (or Kosmos 557), and unlike its ill-fated sibling it was a complete success.

[3][4] One of the X-ray telescopes, often called the Filin telescope, consisted of four gas flow proportional counters, three of which had a total detection surface of 450 cm2 in the energy range 2–10 keV, and one of which had an effective surface of 37 cm2 for the range 0.2 to 2 keV (32 to 320 aJ).

[1] Other instruments include a swivel chair for vestibular function tests, lower body negative pressure gear for cardiovascular studies, bicycle ergometer integrated physical trainer (electrically driven running track 1 m X .3 m with elastic cords providing 50 kg load), penguin suits and alternate athletic suit, sensors for temperature and characteristics of upper atmosphere, ITS-K infrared telescope spectrometer and ultraviolet spectrometer for study of earth's infrared radiation, multispectral earth resources camera, cosmic ray detector, embryological studies, new engineering instruments tested for orientation of station by celestial objects and in darkness and a teletypewriter.

A highly variable low energy of 0.6 to 0.9 keV (96 to 144 aJ) flux was detected in Sco X-1.

Cir X-1 was not detected at all during a July 5, 1975 observation, providing an upper limit on the emission of 3.5e-11 erg·cm−2·s−1 (35 fW/m2) in the 0.2 to 2.0 keV (32 to 320 aJ) range.