Future Missions

The next two decades of astronomy are already being built. Across four continents, telescopes are under construction that will dwarf every instrument that came before them. In clean rooms and integration facilities, spacecraft are being assembled for journeys to moons that may harbor life. On drawing boards and in simulation laboratories, mission concepts are being refined that could detect biosignatures on exoplanets, map the gravitational wave universe, and resolve the first structures that formed after the Big Bang. The pipeline of future missions represents the most ambitious era of astronomical investment in history, driven by questions that current instruments have raised but cannot answer.

Ground-Based Telescopes: The Extremely Large Generation

Three telescopes under construction will constitute the next generation of ground-based optical/infrared astronomy. Each uses a segmented primary mirror far larger than any existing telescope, combined with adaptive optics systems that correct for atmospheric distortion in real-time, achieving angular resolution that rivals or exceeds space-based instruments at certain wavelengths.

The Extremely Large Telescope (ELT), under construction by the European Southern Observatory on Cerro Armazones in Chile's Atacama Desert, will have a 39.3-meter primary mirror composed of 798 hexagonal segments. First light is expected in the late 2020s. The ELT's light-collecting area is roughly 13 times that of the largest current optical telescopes (the 10-meter Keck telescopes) and over 250 times that of Hubble. Its adaptive optics system will deliver diffraction-limited imaging, resolving features as small as a few milliarcseconds.

The ELT's science case spans every area of astronomy. It will directly image exoplanets that are too faint for current telescopes, characterize their atmospheres through high-resolution spectroscopy, resolve individual stars in galaxies beyond the Local Group, study the first galaxies at the highest redshifts, and measure the expansion rate of the universe in real-time by tracking the drift of quasar absorption lines over years (the Sandage-Loeb test).

The Thirty Meter Telescope (TMT), a partnership among Caltech, the University of California, Canada, China, India, and Japan, will have a 30-meter segmented primary mirror. Originally planned for Mauna Kea in Hawaii, the project faced sustained opposition from Native Hawaiian cultural practitioners and activists who consider the summit sacred. The TMT consortium has explored the alternative site of Roque de los Muchachos on La Palma in the Canary Islands while continuing efforts toward the Mauna Kea site. The resolution of the siting dispute remains uncertain.

The Giant Magellan Telescope (GMT), under construction at Las Campanas Observatory in Chile, uses a different optical design: seven 8.4-meter monolithic mirrors arranged in a flower-petal configuration, giving an effective aperture of 24.5 meters. The GMT's resolution at its diffraction limit will exceed Hubble's by a factor of ten. First light is expected in the late 2020s with an initial complement of four mirrors, with the full seven-mirror array completed later.

Together, these three telescopes will transform ground-based astronomy. Their combined capabilities in direct exoplanet imaging, high-resolution spectroscopy, and faint-object detection will complement JWST and its successors, providing observational power at optical and near-infrared wavelengths that no space telescope currently planned can match.

The Vera C. Rubin Observatory and LSST

The Vera C. Rubin Observatory, under construction on Cerro Pachon in Chile, will conduct the Legacy Survey of Space and Time (LSST), the most ambitious ground-based astronomical survey ever attempted. Using an 8.4-meter primary mirror and a 3.2-gigapixel camera (the largest digital camera ever built), the Rubin Observatory will photograph the entire visible southern sky every few nights for ten years, building a time-domain movie of the universe.

LSST will produce roughly 20 terabytes of data per night and generate approximately 10 million transient alerts (objects that have changed brightness or position) each night. The scientific goals include cataloging the solar system's small body population (detecting roughly 100,000 near-Earth asteroids, including potentially hazardous objects), detecting and characterizing millions of supernovae, mapping dark matter through weak gravitational lensing, measuring dark energy through multiple independent methods, and discovering entirely new classes of transient phenomena.

First light is expected in the mid-2020s, with full survey operations beginning shortly after.

Space Telescopes: The Next Generation

The Nancy Grace Roman Space Telescope (formerly WFIRST), scheduled for launch in the mid-2020s, is NASA's next flagship astrophysics mission. Roman has a 2.4-meter primary mirror (the same size as Hubble's, from the same manufacturing heritage) but a field of view 100 times larger than Hubble's, enabling wide-area surveys at Hubble-like resolution. Its primary science goals are measuring dark energy through Type Ia supernova distances, baryon acoustic oscillation measurements, and weak gravitational lensing, and detecting exoplanets through gravitational microlensing and a coronagraphic instrument capable of direct imaging.

The Habitable Worlds Observatory (HWO), recommended as the top priority for a major space mission by the 2020 Astronomy and Astrophysics Decadal Survey (Astro2020), would be a 6-meter-class space telescope optimized for directly imaging Earth-like exoplanets around Sun-like stars and characterizing their atmospheres for biosignatures. HWO would operate at ultraviolet, optical, and near-infrared wavelengths, using a coronagraph to suppress starlight by factors of 10 billion, revealing planets that are a billion times fainter than their host stars. The mission is in early concept development, with launch projected for the 2040s. If funded and built, it would be the most capable exoplanet characterization instrument ever constructed.

ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey), an ESA medium-class mission scheduled for launch in 2029, will conduct a systematic spectroscopic survey of roughly 1,000 exoplanet atmospheres, building the first statistical sample of atmospheric compositions across the exoplanet population.

PLATO (PLAnetary Transits and Oscillations of Stars), an ESA mission scheduled for launch in 2026, will search for rocky exoplanets in the habitable zones of Sun-like stars using ultra-precise transit photometry from 26 cameras, while simultaneously characterizing the host stars through asteroseismology.

Gravitational Wave Detectors

LISA (Laser Interferometer Space Antenna), an ESA-led mission with NASA participation scheduled for the mid-2030s, will be the first space-based gravitational wave observatory. Three spacecraft in a triangular formation, separated by 2.5 million kilometers, will detect gravitational waves in the millihertz frequency band, opening a window onto supermassive black hole mergers, compact binary systems in the Milky Way, extreme mass-ratio inspirals, and potentially primordial gravitational waves from the early universe.

Einstein Telescope and Cosmic Explorer are proposed next-generation ground-based gravitational wave detectors that would improve sensitivity by an order of magnitude over Advanced LIGO, detecting essentially every compact binary merger in the observable universe.

CMB-S4, a comprehensive ground-based cosmic microwave background experiment combining multiple observatories, will search for the primordial B-mode polarization signal predicted by inflationary theory, constrain neutrino masses, and map the large-scale structure of the universe through CMB lensing.

Planetary Science and Solar System Exploration

Europa Clipper (launched 2024, arrival at Jupiter ~2030) will conduct detailed flybys of Jupiter's moon Europa to characterize its ice shell, subsurface ocean, and potential habitability.

Dragonfly, a NASA New Frontiers mission, will send a rotorcraft lander to Saturn's moon Titan in the mid-2030s to explore its surface chemistry, study prebiotic chemical processes, and search for signs of past or present biological activity in an environment rich in organic molecules and liquid hydrocarbons.

Mars Sample Return remains a priority for planetary science, with Perseverance currently collecting and caching samples in Jezero Crater. The return architecture, involving a lander, ascent vehicle, and Earth return orbiter, has faced significant budget and schedule challenges. Alternative architectures involving commercial partners are being explored.

Uranus Orbiter and Probe, identified as the top priority for a new flagship planetary mission by the 2023-2032 Planetary Science and Astrobiology Decadal Survey, would provide the first dedicated orbital investigation of an ice giant. The mission would study Uranus's atmosphere, interior structure, ring system, magnetosphere, and moons. No mission has been formally approved, but the decadal endorsement carries significant weight in NASA's planning.

JUICE (Jupiter Icy Moons Explorer), an ESA mission launched in 2023, will arrive at Jupiter in 2031 and eventually enter orbit around Ganymede, the solar system's largest moon, becoming the first spacecraft to orbit a moon other than Earth's.

The Decade Ahead

The common thread across these missions is ambition calibrated to specific questions. The ELTs will resolve what current telescopes cannot. Rubin will discover what snapshot surveys miss. Roman will map the dark universe with statistical power that Hubble cannot approach. HWO will search for life on other worlds with instruments designed for that singular purpose. LISA will hear the gravitational wave universe across frequencies that ground-based detectors cannot reach. Europa Clipper and Dragonfly will go where the astrobiology points.

Not all of these missions will survive to completion. Budget pressures, technical challenges, and political priorities will thin the pipeline. But the scientific questions driving them, Is there life beyond Earth? What is dark energy? How did galaxies form? What happens when spacetime is most extreme? are the right questions, and the instruments being built to answer them represent the most capable astronomical toolkit ever assembled.