Exploring Space: Stations, Telescopes and Missions
People explore space by looking from the ground, by putting telescopes above the air, by sending robots to fly past, orbit and land on other worlds, and by living on a space station you can see from Guyana.
Related: Orbits, Gravity and Satellites · ISS Pass Predictor · Planets Visible Tonight
This lesson is mapped to objective SO 1.5 of the CSEC Integrated Science syllabus, human exploration of the universe; it is not endorsed by CXC or the Ministry of Education. Teachers: the Teacher Page for CSEC sets this lesson beside the other four objectives, with class sheets dated for Guyana. Mission facts come from NASA and the European Space Agency (ESA), named beside each one; naming them implies no endorsement by either. All times on this page are Guyana time (America/Guyana, UTC-4, no daylight saving). Georgetown numbers use 6.80° N, 58.16° W. Lethem numbers use 3.38° N, 59.80° W.
Ways to explore space
Most of what we know about space comes from light: we look. When looking from the ground is not enough, we send machines, and sometimes people.
- Telescopes on the ground collect more light than the eye. From Guyana, binoculars already show Jupiter's four big moons and craters on the Moon.
- Telescopes in space sit above the air, which blurs starlight and blocks most infrared and ultraviolet light.
- A flyby passes close to a world once, taking pictures and measurements on the way past.
- An orbiter goes into orbit around a world and studies it for years.
- A lander sets down on the surface. A rover is a lander on wheels that drives from place to place.
- Humans travel there themselves. So far people have stood only on the Moon.
| Kind of mission | An example | When | |---|---|---| | Flyby | Mariner 4 flew past Mars and sent back the first close-up pictures of another planet | 14 July 1965 | | Flyby | Voyager 1 flew past Jupiter, about 280,000 km away at its closest | 5 March 1979 | | Orbiter | Juno went into orbit around Jupiter, and is still studying it | 4 July 2016 | | Lander and rover | Perseverance landed in Jezero Crater on Mars | 18 February 2021 | | Humans | Apollo 11: the first people walked on the Moon | 20 July 1969 |
Dates from NASA's mission pages (US dates). Twelve people walked on the Moon in the Apollo missions, the last in December 1972. Nobody has yet been to Mars.
Scientists want to drive across the floor of a crater on Mars, stopping to drill rocks. Which kind of mission do they need?
- A flyby
- An orbiter
- A rover (the right answer)
- A ground telescope in Guyana
A rover. A flyby passes once, an orbiter stays high above, and a telescope on Earth is far too far away. Only a rover can drive from rock to rock.
The International Space Station
The International Space Station (ISS) is a laboratory where astronauts from several countries live and work. Its parts were launched from 1998 and joined together in orbit. People have lived on board without a break since 2 November 2000.
From NASA's figures:
- It orbits between 370 and 460 km above the ground.
- It goes round Earth about every 90 minutes, about 16 times a day.
- It travels at about 8 km a second (five miles a second).
- It has a mass of about 420,000 kg.
The station's height is about the same as the straight-line distance from Georgetown to Lethem, about 420 km.
You can see the ISS from Guyana with your own eyes. It looks like a bright, steady star gliding across the sky in a few minutes, with no flashing lights. It shines because it is still in sunlight high above you after your sky has gone dark.
Earth and its shadow to scale: why a station 420 km up shines in a dark sky, and when it goes dark.
The coming passes for Georgetown or Lethem as the ISS Pass Predictor finds them, with each pass's path on a compass dial.
The video Why the ISS vanishes shows a pass fading out as the station enters Earth's shadow.
Why is the ISS seen only for a few hours after sunset or before sunrise, and not at midnight?
- It switches its lights off at midnight
- At midnight the station is in Earth's shadow, so no sunlight reaches it (the right answer)
- It is below the horizon of the whole Earth at midnight
- Clouds always cover the sky at midnight
The ISS has no lights bright enough to see. It shines by reflected sunlight. Near midnight both you and the station are in Earth's shadow.
Telescopes above the air: Hubble and James Webb
The air blurs starlight, which is why stars twinkle, and it blocks most infrared and ultraviolet light. A telescope in space sees sharper pictures and light that never reaches the ground.
| | Hubble Space Telescope | James Webb Space Telescope | |---|---|---| | Launched | 24 April 1990, by the Space Shuttle Discovery | 25 December 2021, on an Ariane 5 rocket from Europe's Spaceport in French Guiana | | Where it is | Orbiting Earth about 483 km up, once every 95 minutes | Orbiting the Sun near a point called L2, 1.5 million km from Earth | | Main mirror | 2.4 m across | 6.5 m across, made of 18 segments | | Light it sees | Ultraviolet, visible and near-infrared light | Infrared light |
Hubble from NASA's Hubble pages; Webb's launch from ESA, its place and mirror from NASA.
Hubble's orbit is tilted 28.5° to the equator, so it passes over places from 28.5° N to 28.5° S, Guyana included. Webb is about 3,000 times farther from Earth than Hubble. Hubble is far enough out to escape the air, but it is not far away: it orbits only a little higher than the ISS.
Webb's longer infrared waves pass through dust that hides newborn stars, and let it see light from very distant galaxies, stretched into the infrared on its long journey to us.
Where is the James Webb Space Telescope?
- In a low orbit around Earth, like Hubble
- On the Moon
- Orbiting the Sun near L2, about 1.5 million km from Earth (the right answer)
- On a mountain top in South America
Webb orbits the Sun near the point called L2, about 1.5 million km from Earth, far beyond the Moon.
See their pictures
The syllabus asks students to look at photographs from both telescopes. NASA publishes them free on its own pages:
Credit the images to NASA (and its partners named on each picture) when you use them in class.
Missions to Mars and Jupiter
Mars
Mars is the planet people have explored most with robots.
- Flyby: Mariner 4, July 1965, the first close-up pictures.
- Orbiter: NASA's Mars Reconnaissance Orbiter reached Mars on 10 March 2006. It maps the planet from above and passes messages from other Mars missions back to Earth.
- Lander and rover: Perseverance launched on 30 July 2020 and landed in Jezero Crater on 18 February 2021, about seven months later. It searches for signs of ancient life and collects rock samples.
- Humans: none yet.
Jupiter
Jupiter is a giant ball of gas and liquid with no solid ground to land on, so its explorers fly past it or orbit it.
- Flybys: Voyager 1 passed it on 5 March 1979.
- Orbiter: Juno launched on 5 August 2011 and went into orbit on 4 July 2016, almost five years later.
- Europa Clipper (NASA) launched on 14 October 2024 to study Europa, an icy moon of Jupiter with an ocean under its ice. It is due at Jupiter in April 2030.
- Juice (ESA) launched on 14 April 2023 on an Ariane 5 from Europe's Spaceport in French Guiana, to study Jupiter's icy moons. It is due at Jupiter in July 2031.
Jupiter is so far away that a trip takes five to eight years.
Both planets are often easy to see from Guyana. Find them tonight, then think of the spacecraft there right now.
Tonight's sky over Georgetown or Lethem with the ecliptic drawn in: find Mars and Jupiter, and the other planets, on or near it.
Guyana's neighbour in space
Europe's Spaceport, the Guiana Space Centre at Kourou in French Guiana, is about 620 km east-south-east of Georgetown. ESA gives its latitude as 5°3' N. Near the equator Earth's spin gives a rocket a free push of about 460 m/s. Both the James Webb Space Telescope and Juice began their journeys there, on South America's north coast.
Try it: plan a mission
Work in groups of three or four.
- Pick a target: Mars, Jupiter, or Jupiter's moon Europa.
- Pick the kind of mission: flyby, orbiter, lander, rover or humans. Use the table above to decide what each can and cannot do.
- Write the one question your mission will answer, for example "Was there ever water on this world?"
- List what can go wrong: distance and travel time, radiation, cold, no air, landing on rough ground, and for humans food, water and the long trip home.
- Present your mission in two minutes. The class votes on which question is most worth answering.
View the pictures. Open NASA's Webb and Hubble image pages above. Find one object both telescopes have photographed, and describe what each picture shows that the other does not.
See the station. Use the ISS Pass Predictor to find a pass worth going out for. Write down the time it appears, the direction, how high it climbs in fists at arm's length, and the time it fades or sets.
Common mix-ups
"Hubble is far out in space." No. Hubble orbits about 483 km up, a little higher than the ISS. It is above the air, which is what matters for a telescope.
"The James Webb telescope orbits Earth." No. Webb orbits the Sun near L2, about 1.5 million km from Earth, almost four times as far as the Moon.
"Astronauts have been to Mars." No. People have stood only on the Moon. Mars has been explored by flybys, orbiters, landers and rovers.
Quick check
Why were Hubble and Webb put in space instead of on a high mountain?
- Stars are closer to a telescope in space
- Above the air, pictures are not blurred, and infrared and ultraviolet light are not blocked (the right answer)
- Telescopes on the ground cannot see at night
- It is cheaper to build a telescope in space
The air blurs starlight and blocks most infrared and ultraviolet light. Even the highest mountain has air above it; space has none.
Where next
Go back over how satellites stay up in ASTRO-106: Orbits, Gravity and Satellites, or take a telescope outside with ASTRO-108: First Telescope Night.