How Many Telescopes Are In Space

by

If you’ve ever looked up at the night sky and wondered about our tools for seeing deeper, you might ask a specific question: how many telescopes are in space? The answer is more fascinating and complex than a simple number, as it depends on what you count as a “telescope.” This article will guide you through the current fleet of cosmic observatories, from famous ones like Hubble to tiny cubesats, explaining what they do and why they’re there.

Our view from Earth is limited by our atmosphere, which blurs light and blocks many types of radiation. Space telescopes provide a crystal-clear window to the universe. They detect not just visible light, but also X-rays, gamma rays, infrared, and radio waves. This lets scientists study everything from black holes to the birth of planets.

So, let’s start counting. We’ll break it down by type and mission to give you a clear picture of humanity’s eyes in the sky.

How Many Telescopes Are In Space

As of late 2024, there are over 100 active space-based telescopes and observatories. This number includes major NASA, ESA, and JAXA missions, as well as numerous smaller satellites from universities and private companies. The count fluctuates as old missions end and new ones launch. It’s important to note that this includes spacecraft whose primary job is astronomy. It does not include Earth-observation satellites (like weather satellites) or navigational satellites, even though they use similar technology.

Major Operational Space Telescopes (The Heavy Hitters)

These are the flagship missions, often decades in the making, that have revolutionized our understanding.

  • The Hubble Space Telescope (NASA/ESA): Launched in 1990, it’s perhaps the most famous. Orbiting Earth, it observes in visible, ultraviolet, and near-infrared light. It’s responsible for countless iconic images and major discoveries, like the accelerating expansion of the universe.
  • The James Webb Space Telescope (NASA/ESA/CSA): Launched in 2021, Webb is Hubble’s successor but operates very differently. It sits at a point called L2, far from Earth, and specializes in infrared light. This allows it to see the first galaxies and peer into dusty stellar nurseries.
  • The Chandra X-ray Observatory (NASA): Launched in 1999, Chandra sees the high-energy universe—hot gas from exploded stars, matter swirling into black holes, and galaxy clusters. It’s orbit takes it one-third of the way to the moon.
  • XMM-Newton (ESA): Also an X-ray telescope launched in 1999, it complements Chandra by being able to collect more light over a wider field, great for surveying the sky.
  • The Fermi Gamma-ray Space Telescope (NASA): Operating since 2008, Fermi scans the entire sky every three hours, detecting the most energetic form of light. It studies gamma-ray bursts, pulsars, and the jets of active galaxies.
  • Swift Observatory (NASA): Launched in 2004, it’s designed to quickly detect and pinpoint gamma-ray bursts, then swivel to observe them with other instruments.
  • TESS (Transiting Exoplanet Survey Satellite) (NASA): Since 2018, TESS has been scanning nearly the entire sky to find planets orbiting bright nearby stars, identifying thousands of exoplanet candidates.
  • Gaia (ESA): Launched in 2013, Gaia is mapping over a billion stars in our Milky Way with incredible precision, creating a 3D atlas of our galaxy and measuring there motions.

Specialized and Smaller Missions

Beyond the flagships, many missions target specific questions or use new technologies.

  • NuSTAR (NASA): Focuses on high-energy X-rays, revealing the inner workings of supernovae and the surroundings of black holes.
  • NICER (NASA): An instrument on the International Space Station studying neutron stars.
  • Hinode (JAXA/NASA/ESA): A solar observatory studying the Sun’s magnetic field.
  • Solar Dynamics Observatory (NASA): Provides ultra-high-definition views of the Sun in multiple wavelengths.
  • CHEOPS (ESA): Characterizes known exoplanets by measuring their sizes with high precision.
  • NEOWISE (NASA): An infrared space telescope now dedicated to finding and characterizing asteroids and comets.

The Rise of SmallSats and CubeSats

This is a rapidly growing category. CubeSats are tiny, standardized satellites, often as small as a loaf of bread. Universities and small companies can now afford to launch dedicated space telescopes for focused science.

  • Examples include ASTERIA (a tech demo for exoplanet studies), and SPARCS (a future CubeSat to study volatile stars). Dozens of these are now active or in development, significantly boosting the total count of space telescopes.
  • They often act as pathfinders for new technology or conduct coordinated observations with larger telescopes.

What About Radio Telescopes in Space?

Most radio astronomy is done from the ground because radio waves pass through the atmosphere easily. However, some missions use space to get a wider baseline or avoid human-made interference.

  • Spektr-R (RadioAstron): This was a Russian-led mission that combined with ground telescopes to form a virtual dish the size of Earth’s orbit. It’s now defunct, but it demonstrated the power of space-based radio interferometry.
  • Future missions are being planned to place radio telescopes on the far side of the Moon, which is permanently shielded from Earth’s radio noise.

Why the Exact Number is Fuzzy

Getting a single, definitive number is tricky for a few reasons.

  1. Definition: Is a satellite with a small lens used for technology testing a “telescope”? The line can be blurry.
  2. Status: Missions can be in standby, partially functional, or in an extended phase. Are they still “active”?
  3. New Launches: With increased launch cadences, new small telescopes go up regularly.
  4. Secrecy: Some government or military satellites may have astronomical capabilities but their missions are classified and not publicly counted.

Historical and Recently Ended Missions

Many legendary telescopes are no longer operating but their data is still used. They paved the way for current missions.

  • Spitzer Space Telescope (Infrared, ended 2020)
  • Kepler Space Telescope (Exoplanets, ended 2018)
  • Herschel Space Observatory (Far-Infrared, ended 2013)
  • Planck (Cosmic Microwave Background, ended 2013)
  • ROSAT (X-ray, ended 1999)

How Space Telescopes Work (A Simple Breakdown)

Understanding there basic operation helps you see why they’re so special.

1. Getting Above the Atmosphere

The atmosphere distorts light (that’s why stars twinkle) and absorbs certain wavelengths completely. By going to space, telescopes get a steady, clear view across the entire electromagnetic spectrum.

2. Orbit Choices

Different orbits serve different purposes.

  • Low Earth Orbit (LEO): Like Hubble. Easy to service (in theory), but passes through Earth’s shadow and radiation belts frequently.
  • Geosynchronous Orbit: High above a fixed point on Earth. Good for constant communication.
  • Sun-Earth Lagrange Points: Like Webb at L2. These are gravitationally stable points where a spacecraft can “park” with minimal fuel, enjoying a stable thermal environment and an almost uninterrupted view of space.
  • Heliocentric Orbit: Orbiting the Sun, like the Kepler telescope did. This provides a completely stable platform away from Earth’s heat and light.

3. The Instruments

Telescopes carry a suite of instruments, not just cameras.

  1. Cameras/Imagers: Take pictures in specific wavelengths.
  2. Spectrographs: Break light into a rainbow (spectrum) to determine an object’s composition, temperature, and motion.
  3. Photometers: Precisely measure brightness, crucial for finding exoplanets as they transit.
  4. Polarimeters: Measure the orientation of light waves, revealing magnetic field structures.

The Future: What’s Next for Space Telescopes?

The next decade promises an even more incredible array of eyes on the cosmos. Here’s whats coming soon.

Near-Term Launches (Next 5-10 Years)

  • Nancy Grace Roman Space Telescope (NASA): Set to launch around 2027. It will have a field of view 100 times larger than Hubble’s, conducting vast surveys to study dark energy and discover thousands of new exoplanets.
  • PLATO (ESA): An exoplanet hunter focused on finding Earth-like planets in the habitable zone of Sun-like stars. Launch planned for 2026.
  • Euclid (ESA, launched 2023): Now active, it’s mapping the geometry of the dark universe to understand dark matter and dark energy.
  • ARIEL (ESA): Scheduled for 2029, it will perform a chemical census of hundreds of exoplanet atmospheres.

Ambitious Concepts on the Drawing Board

These are larger projects that astronomers are planning for the 2030s and beyond.

  • LUVOIR/HabEx: These are concept studies for large, next-generation telescopes that could directly image Earth-like exoplanets and search for signs of life. They would be significantly larger than Webb.
  • LISA (ESA/NASA): A space-based gravitational wave observatory, designed to detect ripples in spacetime from merging supermassive black holes. Launch expected in the 2030s.
  • Athena (ESA): A large X-ray observatory to study the hot, energetic universe and the evolution of galaxy clusters.

Why So Many? The Power of Multi-Wavelength Astronomy

You might wonder why we need so many different telescopes. The key is that different cosmic phenomena emit different types of light. To get the full picture, you need to observe across the spectrum.

  • Example – A Supernova Remnant: Chandra sees the million-degree shock waves (X-rays). Hubble sees the expanding debris shell (visible light). Spitzer would have seen the warm dust (infrared). Together, they tell the complete story of the star’s death.
  • Example – A Black Hole’s Disk: X-rays come from the hot inner disk. Visible/UV light comes from the outer disk. Radio waves often come from the jets. Observing with multiple telescopes simultaneously is like having a multi-sensory view of the event.

Coordinated Observing Campaigns

Scientists often point many telescopes, both in space and on the ground, at a single target at the same time. This global (and beyond) coordination is a cornerstone of modern astrophysics and yields the richest data.

FAQ: Your Questions Answered

What is the most powerful telescope in space right now?

For infrared astronomy, the James Webb Space Telescope is the most powerful ever launched. For visible light, Hubble remains extremely powerful, though the newer Roman Telescope will have a wider field. “Power” depends on the wavelength and type of science being done.

How many space telescopes does NASA have?

NASA currently operates over two dozen active space telescope missions, not including instruments on the ISS or partnerships where NASA contributes to another agency’s telescope (like Webb or Gaia).

Are there any space telescopes looking at Earth?

Technically, yes—Earth-observation satellites use telescope optics. But in astronomy, “space telescope” usually refers to instruments pointed away from Earth, toward the cosmos. Those dedicated to Earth science are a separate, and much larger, fleet.

Can I use a space telescope for my project?

Yes, but through a competitive proposal process. Astronomers from around the world submit requests for time on telescopes like Hubble or Webb. A panel of experts reviews the proposals and awards time based on scientific merit. Some smaller satellite data is also publicly available.

What happens to old space telescopes?

It depends on there orbit. Those in low Earth orbit, like Hubble, will eventually re-enter Earth’s atmosphere and burn up, though Hubble may be de-orbited controllably in the future. Telescopes at Lagrange points or in solar orbit are usually left there, placed in a safe “graveyard” state after there fuel is exhausted. They become inert pieces of space history.

How much does a space telescope cost?

Costs vary wildly. Flagship missions like Webb cost about $10 billion over its lifetime. Smaller explorers like TESS cost around $200 million. CubeSats can be built and launched for under $10 million. The price reflects size, complexity, instruments, and launch vehicle.

Conclusion: A Growing Cosmic Network

So, back to our initial question: how many telescopes are in space? The robust answer is over 100 active astronomical observatories, with the number growing each year thanks to smaller, more affordable satellites. This network, working across all light’s wavelengths, forms humanity’s collective vision into the universe. Each telescope, from the massive Webb to a tiny CubeSat, plays a unique role in piecing together the story of the cosmos, from it’s beginning to it’s possible futures.

Next time you see a stunning space image, remember it’s likely the product of not just one, but several of these incredible machines working in concert. And with new missions always on the horizon, our view of the universe will only get sharper, wider, and more profound. The journey to understand our place in the cosmos continues, one telescope at a time.