EUSO was a mission of the European Space Agency, designed to be hosted on the International Space Station as an external payload of the Columbus. EUSO successfully completed the "Phase A" study, however in 2004, ESA decided not to proceed with the mission because of programmatic and financial constraints. The mission was then re-oriented as a payload to be hosted on board the JEM module of the Japanese KIBO facility of the ISS. The mission was then renamed JEM-EUSO.
JEM-EUSO
JEM-EUSO is currently studied by RIKEN and JAXA, in collaboration with 95 other institutions from 16 countries aiming for a flight after 2020. The proposed instrument consists of a set of three large Fresnel lenses of 2.65-metre diameter feeding a detector consisting of 137 modules each a 48 x 48 array of photomultipliers. The imaging takes place in the 300 nm-450 nm band, and photons are time-tagged with 2.5-microsecond precision.
In addition to its main, science mission, EUSO might also be used to detect orbiting space junk that could pose a threat to ISS, but is too small to be spotted by astronomers. The ISS is shielded adequately against particles that are smaller than 1 cm. Particles in this range, or larger, can inflict serious damage, especially to other objects in orbit, since many of them are traveling at speeds of about 36,000 km/h. Nearly 3,000 tons of space debris resides in low-Earth orbit; more than 700,000 pieces of debris larger than 1 cm now orbit Earth. A laser might then be used to deflect dangerous particles. The project could be ready to implement after about 2017–2018, using better lasers.
EUSO-Balloon: a balloon-based EUSO telescope meant to further validate the technology. The balloon flight took place in 2014 in Canada and lasted 5 hours. The telescope observed laser-simulated cosmic ray events.
EUSO-SPB : a high-altitude heavy-lift balloon EUSO telescope. Launched in 2017 from New Zealand. The flight took 13 days, but was cut substantially shorter than the planned 100 days. Second mission is planned for 2021.
TUS : a Russian mission on board the Lomonosov-satellite ; included in the EUSO program as of 2018.
Mini-EUSO: an ultraviolet telescope operated at the ISS. The telescope serves as a pathfinder mission for UCHER-missions in space and maps the ultraviolet background produced by Earth atmosphere. The mapping of the UV-background is important for the follow-up missions K-EUSO and JEM-EUSO. The mission started as a co-operation between Italian Space Agency and Russian Space Agency. The Mini-EUSO telescope was launched to ISS on 22 August 2019.
K-EUSO : a Russian Space Agency project to place an UHECR telescope in the Russian segment of ISS. The project builds upon the TUS-experiment of the Russian Lomonosov-satellite. In 2017, the launch was scheduled for 2022.
JEM-EUSO : the final goal of the JEM-EUSO program is to have the JEM-EUSO telescope installed into ISS.
POEMMA : a dedicated satellite mission to observe UHECR-events in the atmosphere. As of 2018, it is a NASA-sponsored concept study.
