Ariel 5 (or UK 5) was a joint British and American space telescope dedicated to observing the sky in the X-ray band.

[4] A study was performed to see if the Scout rocket's heat shield could be enlarged to accommodate larger experiments for this mission.

[7] The all-sky monitor (ASM) was two one-dimensional pinhole cameras scanned most of the sky every spacecraft revolution.

The ASM was designed to fit a resource budget of 2 kg (4.4 lb), 1 bit per second, and 1 W.[8] The sky survey instrument (SSI) had an angular resolution of 0.75 × 10.6°, with an effective area of 290 cm2 (45 sq in), and a bandpass of 2–20 keV.

[9] The satellite was launched on 15 October 1974 from the San Marco platform in the Indian Ocean off the coast of Kenya.