[7] SPICA would have improved on the spectral line sensitivity of previous missions, the Spitzer and Herschel space telescopes, between 30 and 230 μm by a factor of 50—100.

[8] A final decision was expected in 2021,[4] but in October 2020, it was announced that SPICA was no longer being considered as a candidate for the M5 mission.

[9][10] In Japan, SPICA was first proposed in 2007, initially called HII-L2 after the launch vehicle and orbit, as a large Strategic L-class mission,[11][12][13] and in Europe it was proposed to ESA's Cosmic Vision programme (M1 and M2),[11] but an internal review at ESA at the end of 2009 suggested that the technology readiness for the mission was not adequate.

It would have been able to detect stellar nurseries in galaxies, protoplanetary discs around young stars, and exoplanets, helped by its own coronograph for the latter two types of objects.

The design featured V-groove radiators and mechanical cryocoolers rather than liquid helium to cool the mirror to below 8 K (−265.15 °C)[2] (versus the 80 K or so of a mirror cooled only by radiation like Herschel's) which provides substantially greater sensitivity in the 10–100 μm infrared band (IR band); the telescope was intended to observe infrared light at longer wavelengths than the James Webb Space Telescope.