Operated by the European Space Research Organisation, TD-1A made astronomical surveys primarily in the ultraviolet, but also using x-ray and gamma ray detectors.

[9] Spectrometry of Celestial X-Rays was another payload operated by the Saclay Nuclear Research Centre.

It consisted of two slot collimators and a proportional counter, which were used to study the spectra of incident x-rays.

[12] The Saclay Nuclear Research Centre's Gamma-Ray Measurement experiment used a spark chamber to detect gamma rays during the sky survey.

[5][14] TD-1A was affected by reliability issues with an onboard tape recorder, used to store experimental data for transmission to Earth, however the fault was intermittent, and still enabled the completion of the spacecraft's mission.

[10] In May 1974, TD-1A ceased operations when its attitude control system depleted its last remaining propellant, leaving it unable to maintain its orientation.