The Ultraviolet Explorer (UVEX) is an upcoming wide-field

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

space telescope A space telescope (also known as space observatory) is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO ...

from

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

scheduled to launch in 2030. UVEX will build off of previous ultraviolet space telescopes, specifically

GALEX Galaxy Evolution Explorer (GALEX or Explorer 83 or SMEX-7) was a NASA orbiting space telescope designed to observe the universe in ultraviolet wavelengths to measure the history of star formation in the universe. In addition to paving the way ...

, conducting surveys of the entire sky in both near- and far-ultraviolet light. UVEX will study the evolution of low-metallicity stars and how they affect the evolution of low-metallicity and low-mass galaxies. The probe can also be used for quick-turnaround observation of cosmic events, such as merging stars. UVEX's data will be able to complement other all-sky survey programs in different wavelengths of light, notably those by the Vera C. Rubin Observatory, the

Nancy Grace Roman Space Telescope The Nancy Grace Roman Space Telescope (shortened as the Roman Space Telescope, Roman, or RST) is a NASA infrared space telescope in development and scheduled to launch to a Sun–Earth L2 orbit by May 2027. It is named after former NASA Chie ...

, and

Euclid Euclid (; ; BC) was an ancient Greek mathematician active as a geometer and logician. Considered the "father of geometry", he is chiefly known for the '' Elements'' treatise, which established the foundations of geometry that largely domina ...

. Compared to earlier ultraviolet space telescopes, UVEX will feature more capable instrumentation and a larger mirror, enabling it to obtain higher-resolution data and observe fainter objects.

Spacecraft

Science payload

UVEX will contain one instrument, consisting of the UV-optimized optical telescope array (OTA) and the UV Instrument Module (UVIM). The OTA consists of a -diameter primary mirror in a three-mirror anastigmat configuration which will capture and redirect light to three different sensors. * Two of these belong to the imager, with one featuring coatings to only accept near-ultraviolet (NUV) light, with its counterpart accepting only far-ultraviolet (FUV) light. Both sensors, each consisting of nine 4k x 4k CMOS detectors arranged in a 3 x 3 pattern, are identical apart from their coatings and will receive light from a dichroic, which splits the light beam from the OTA to send each sensor its corresponding wavelengths of light. The dichroic allows both sensor assemblies to image simultaneously. Due to the low focal ratio of the OTA and the large sensors, the imager can capture 3.5° x 3.5° images of the sky at once. *The third sensor, a single 4k x 4k detector, belongs to the long-slit spectrograph. Light from the OTA would reach the detector by bypassing the dichroic and passing through the slit and grating. The spectrograph has a length of 2° and can achieve a maximum resolving power of roughly R = 3500.

Spacecraft bus

Mission

UVEX is classified as a Medium-Class Explorer (MIDEX) in NASA's Explorers Program and is planned to launch in 2030. After a period of orbit corrections and instrument commissioning, the probe will begin a two-year series of full-sky surveys. Because of its larger primary mirror, which can capture more light at once than the smaller mirrors of its predecessors, UVEX will observe dimmer and further objects. The probe will reach

AB magnitude The AB magnitude system is an astronomical magnitude system. Unlike many other magnitude systems, it is based on flux measurements that are calibrated in absolute units, namely spectral flux densities. Definition The ''monochromatic'' AB magn ...

s greater than 25.8, comparable to the ground-based Vera C. Rubin Observatory. UVEX will also perform weekly surveys of the

Magellanic Clouds The Magellanic Clouds (''Magellanic system'' or ''Nubeculae Magellani'') are two irregular dwarf galaxies in the southern celestial hemisphere. Orbiting the Milky Way galaxy, these satellite galaxies are members of the Local Group. Because both ...

, something its predecessors struggled with because of their brightness. UVEX's science goals are divided into three "pillars:" * Study low-metallicity stars and their effects on the evolution of their host galaxies. Low-metallicity low-mass galaxies make up about half of the universe's mass, and they are believed to be very similar to the first galaxies that formed. Studying these objects can give insight into how the first stars and galaxies formed just after the

Big Bang The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including th ...

* Study ongoing and new events in the universe with time-domain surveys, allowing quick follow-up to sudden events like stellar mergers. This will provide additional data to ongoing studies of

gravitational waves Gravitational waves are oscillations of the gravitational field that travel through space at the speed of light; they are generated by the relative motion of gravitating masses. They were proposed by Oliver Heaviside in 1893 and then later by H ...

. * Create a dataset of ultraviolet all-sky surveys for use by current and future scientists, complementing similar surveys by telescopes in other wavelengths of light (primarily

infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

and visible light)

Orbit

UVEX will operate in a highly elliptical lunar resonance orbit called P/2. This type of orbit is currently in use by the TESS spacecraft, which is also performing whole-sky surveys, although TESS is primarily searching for exoplanets. The P/2 orbit is in a 2:1 resonance with the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

, meaning that the spacecraft completes two orbits of Earth for every one orbit of the Moon. Because of this resonance, which enables occasional gravitational interactions with the Moon, the orbit is extremely stable. In addition, the orbit avoids the

Van Allen belts The Van Allen radiation belt is a zone of energy, energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet's magnetosphere. Earth has two such belts, and sometimes ot ...

entirely, drastically reducing wear on spacecraft components. Because of its high altitude and eccentricity, UVEX will take 13.7 days to complete one orbit.

References