If you’ve ever looked up at the stars and wondered about the tools we use to see them clearly, you might ask a specific question: how many space telescopes are there? The answer is more fascinating than a simple number, as it involves active missions, legendary retired observatories, and exciting future projects. This guide will walk you through the current fleet, their incredible history, and what’s coming next.
How Many Space Telescopes Are There
So, how many space telescopes are there right now? As of today, there are over 20 major space telescopes actively collecting data in orbit around Earth or at distant gravitational points. This count includes famous ones like Hubble and James Webb, plus many lesser-known but vital missions from NASA, ESA, JAXA, and other agencies. If we include all past, operational, and planned missions, the total number of space telescope projects throughout history exceeds 150.
The Active Observatory Fleet
Our eyes in the sky are busier than ever. These telescopes don’t just look at visible light; they sense X-rays, gamma rays, infrared, and more. Here’s a list of some key players currently on duty:
- Hubble Space Telescope (HST): Launched in 1990, it’s the legendary workhorse of visible and ultraviolet astronomy.
- James Webb Space Telescope (JWST): The premier infrared observatory, operational since 2022, peering at the first galaxies.
- Chandra X-ray Observatory: Studies violent, high-energy regions of the universe since 1999.
- XMM-Newton: A European X-ray telescope also launched in 1999, with complementary capabilites to Chandra.
- Transiting Exoplanet Survey Satellite (TESS): Hunts for planets around nearby stars since 2018.
- Neil Gehrels Swift Observatory: Detects gamma-ray bursts and rapidly points other instruments at them.
- Solar and Heliospheric Observatory (SOHO): A joint ESA/NASA mission watching the Sun since 1995.
- Solar Dynamics Observatory (SDO): Provides stunning, high-resolution images of our Sun.
- Fermi Gamma-ray Space Telescope: Maps the sky in the highest-energy light.
- Hinode (Solar-B): A Japanese mission studying the Sun’s magnetic fields.
- Astrosat: India’s first multi-wavelength space telescope.
- Gaia: Is creating an unprecedentedly precise 3D map of our Milky Way galaxy.
Understanding the Different Types
Not all space telescopes see the same “light.” Earth’s atmosphere blocks many types of radiation, which is why we need to get above it. Here’s how they break down by what they detect.
Optical and Ultraviolet Telescopes
These observe the light we can see and the ultraviolet rays just beyond blue light. Hubble is the master of this domain. UV light is great for studying hot, young stars and the composition of interstellar gas. Without the atmosphere’s blurring, these telescopes achieve crystal-clear views.
Infrared Telescopes
Infrared light is essentially heat. Telescopes like JWST and the retired Spitzer see through cosmic dust to witness star birth and study cool objects. They must be kept extreamly cold to function properly, often using sunshields and liquid coolant.
X-ray and Gamma-Ray Telescopes
These instruments observe the universe’s most energetic phenomena. They need special grazing-incidence mirrors because these high-energy photons would pass right through normal ones. They show us black holes, neutron stars, and supernova remnants.
A Brief History of Key Missions
The journey to today’s fleet started humbly. The first true space telescope was NASA’s Orbiting Astronomical Observatory 2 (OAO-2), nicknamed Stargazer, which launched in 1968. It proved that complex observations could be done from space. Then came a series of specialized missions.
- 1978: Einstein Observatory (HEAO-2): The first fully imaging X-ray telescope.
- 1983: Infrared Astronomical Satellite (IRAS): The first all-sky infrared survey.
- 1989: Cosmic Background Explorer (COBE): Measured the faint afterglow of the Big Bang.
- 1990: Hubble Launch: After a fix to its flawed mirror, it revolutionized astronomy.
- 1999: Chandra & XMM-Newton: Began the modern era of high-energy astrophysics.
- 2003: Spitzer Space Telescope: Provided deep infrared views for over 16 years.
- 2009: Kepler & Herschel: Kepler found thousands of exoplanets; Herschel studied the cold universe.
- 2021: James Webb Launch: Ushered in a new golden age of infrared astronomy.
Where Are These Telescopes Located?
They aren’t all in the same place. Orbit choice is critical for a telescope’s mission.
- Low Earth Orbit (LEO): About 300-600 km up. Hubble lives here. It’s accessible for servicing but has regular Earth eclipses.
- Geosynchronous Orbit: Much higher, at about 35,000 km. Some solar observatories use this for continuous Sun viewing.
- Lagrange Points: Stable gravitational points in the Sun-Earth system. JWST sits at L2, about 1.5 million km away, for a stable, cold, and unobstructed view.
- Heliocentric Orbit: Orbits around the Sun itself. The retired Kepler telescope was in an Earth-trailing heliocentric orbit.
Future Space Telescopes on the Horizon
The fleet continues to grow. Upcoming missions will push the boundaries even further. Here’s whats in development:
- Nancy Grace Roman Space Telescope: Set to launch around 2027, it will perform wide-field surveys to study dark energy and exoplanets.
- PLATO (ESA): A planet-hunter focused on Earth-like worlds in the habitable zone of Sun-like stars.
- ARIEL (ESA): Will analyze the atmospheres of hundreds of exoplanets.
- LISA (ESA): A space-based gravitational wave observatory, different from light-based telescopes but equally revolutionary.
- Habitable Worlds Observatory (HWO): A NASA concept for a future large telescope designed to directly image and study Earth-like planets.
How Scientists Use the Data
The raw images and spectra from these telescopes are just the start. Teams of researchers around the globe analyze the information. They might:
- Process the raw data to calibrate colors and remove instrument artifacts.
- Compare observations with physcial models of stars, galaxies, or nebulae.
- Combine data from multiple telescopes (like X-ray from Chandra and infrared from JWST) to get a full picture of an object.
- Release the findings in scientific papers and public image releases, which you often see in the news.
Challenges of Operating in Space
It’s not easy running a telescope millions of miles away. Engineers face constant challenges. The space environment is harsh, with extreme temperature swings and radiation that can degrade instruments. Communication delays, especially for telescopes at L2 like JWST, mean commands must be carefully planned. And of course, there’s no chance for a repair mission if something goes wrong with a distant telescope, making redundancy and rigorous testing essential.
How You Can Access the Images
The amazing pictures from these telescopes belong to the public. You can view and even download the raw data yourself. Here’s how:
- Visit the mission’s official website (e.g., Hubble’s Gallery, JWST’s feed).
- Use NASA’s Astroquery tool or the Mikulski Archive for Space Telescopes (MAST).
- Many processed images are available through public outreach sites like NASA’s Astronomy Picture of the Day (APOD).
Common Misconceptions
Let’s clear up a few frequent mix-ups. First, space telescopes are not typically used to look at Earth—that’s the domain of Earth observation satellites. Second, they don’t usually have eyepieces; the light is directed onto digital detectors. Third, while they avoid atmospheric distortion, they are not necessarily always “better” than ground telescopes; large ground-based telescopes with adaptive optics can sometimes match or exceed resolution in certain wavelengths, but space remains essential for blocked parts of the spectrum.
FAQ Section
How many space telescopes are currently active?
Over 20 major space telescopes are actively operating as of the latest count.
What is the total number of space telescopes ever launched?
More than 150 space telescope missions, including small and specialized ones, have been launched since the 1960s.
Which space telescope is the most powerful?
“Powerful” depends on the wavelength. JWST is the most powerful for infrared, Hubble for visible/UV, and Chandra for X-rays.
How many NASA space telescopes are there?
NASA operates or is a major partner in the majority of the active fleet, roughly around 15-18 of the major current missions.
Are there any space telescopes not from NASA?
Yes! Many are from the European Space Agency (ESA), Japan’s JAXA, India’s ISRO, and other national agencies, like the previously mentioned XMM-Newton, Hinode, and Astrosat.
What happens to old space telescopes?
Some are decommissioned and left in a safe orbit, some are steered into a destructive re-entry, and others, like Kepler, are left in a stable heliocentric orbit after running out of fuel.
The Impact on Our Understanding
The collective work of all these telescopes, past and present, has fundamentally changed our place in the cosmos. They’ve confirmed the existence of black holes, measured the age and expansion rate of the universe, discovered thousands of planets beyond our solar system, and captured the iconic images that define our awe of space. Each telescope, with its unique vision, adds a piece to the puzzle. So, when you ask “how many space telescopes are there,” you’re really asking about the number of unique perspectives we have on the universe. And that number is always growing, promising new discoveries for generations to come. The next time you see a stunning space image, remember the fleet of robotic explorers, silently watching the heavens, that made it possible.