Callirrhoe.space

Spacewatch: the survey that found Callirrhoe

Founded in 1980, Spacewatch has hunted asteroids and comets from Kitt Peak for longer than any similar program still running.

Published 2026-10-23

Callirrhoe was a by-product of a survey built to find something else: asteroids and comets.[5][2]

Origins

Spacewatch was founded in 1980 by Tom Gehrels and Robert S. McMillan at the University of Arizona. It has been active longer than any other similar program still operating, and is now led by Melissa Brucker.[5]

The telescopes

Spacewatch uses three telescopes on Kitt Peak, of 0.9, 1.8 and 2.3 metres aperture.[5] The 36-inch (0.9 m) telescope has been used since 1984 — the instrument that caught Callirrhoe.[5][2] The 1.8 m Spacewatch telescope is described as the largest in the world used exclusively for asteroids and comets.[5]

Why surveys find moons

Wide-field CCD cameras, which replaced photographic plates in the 1990s, could cover large areas of sky at new sensitivity.[4] A survey sweeping past Jupiter can pick up faint moons as well as asteroids — which is exactly what happened in 1999.[4]

Numbered citations link to the sources list on the Callirrhoe overview page.

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