How to catch a satellite
Standard space dockings are difficult enough, but a future ESA mission plans to capture derelict satellites adrift in orbit. Part of an effort to control space debris, the shopping list of new technologies this ambitious mission requires is set for discussion with industry experts.
ESA’s Clean Space initiative is studying the e.DeOrbit mission for removing debris, aiming to reduce the environmental impact of the space industry on Earth and space alike.
Decades of launches have left Earth surrounded by a halo of space junk: more than 17 000 trackable objects larger than a coffee cup, which threaten working missions with catastrophic collision. Even a 1 cm nut could hit with the force of a hand grenade.
The only way to control the debris population across key low orbits is to remove large items such as derelict satellites and launcher upper stages.
Such uncontrolled multi-tonne items are not only collision risks but also time bombs: they risk exploding due to leftover fuel or partially charged batteries heated up by orbital sunlight.
The resulting debris clouds would make these vital orbits much more hazardous and expensive to use, and follow-on collisions may eventually trigger a chain reaction of break-ups.
e.DeOrbit is designed to target debris items in well-trafficked polar orbits, between 800 km to 1000 km altitude. At around 1600 kg, e.DeOrbit will be launched on ESA’s Vega rocket.
The first technical challenge the mission will face is to capture a massive, drifting object left in an uncertain state, which may well be tumbling rapidly. Sophisticated imaging sensors and advanced autonomous control will be essential, first to assess its condition and then approach it.
Making rendezvous and then steady stationkeeping with the target is hard enough but then comes the really difficult part: how to secure it safely ahead of steering the combined satellite and salvage craft down for a controlled burn-up in the atmosphere?
Several capture mechanisms are being studied in parallel to minimise mission risk. Throw-nets have the advantage of scalability – a large enough net can capture anything, no matter its size and attitude. Tentacles, a clamping mechanism that builds on current berthing and docking mechanisms, could allow the capture of launch adapter rings of various different satellites.
Harpoons work no matter the target’s attitude and shape, and do not require close operations. Robotic arms are another option: results from the DLR German space agency’s forthcoming DEOS orbital servicing mission will be studied with interest.
Strong drivers for the platform design are not only the large amount of propellant required, but also the possible rapid tumbling of the target – only so much spin can be absorbed without the catcher craft itself going out of control.
Apart from deorbit options based on flexible and rigid connections, techniques are being considered for raising targets to higher orbits, including tethers and electric propulsion.
TOP IMAGE…One capture concept being explored through ESA’s e.Deorbit system study for Active Debris Removal - capturing the satellite in a net attached to either a flexible tether (as seen here) or a rigid connection. Copyright ESA
CENTRE IMAGE…Simulations of orbital debris show that actively removing large items of debris, such as entire derelict satellites, should help stabilise its population and prevent a collision-based cascade effect. ESA has performed a system study for an Active Debris Removal mission called e.Deorbit. Copyright ESA
LOWER IMAGE…All human-made space objects result from the near-5000 launches since the start of the space age. About 65% of the catalogued objects, however, originate from break-ups in orbit – more than 240 explosions – as well as fewer than 10 known collisions. Scientists estimate the total number of space debris objects in orbit to be around 29 000 for sizes larger than 10 cm, 670 000 larger than 1 cm, and more than 170 million larger than 1 mm.
Any of these objects can cause harm to an operational satellite. For example, a collision with a 10 cm object would entail a catastrophic fragmentation of a typical satellite, a 1 cm object will most likely disable a spacecraft and penetrate the International Space Station shields, and a 1 mm object could destroy subsystems. Scientists generally agree that, for typical satellites, a collision with an energy-to-mass ratio exceeding 40 J/g would be catastrophic. Copyright ESA
These fun illustrations by Norbert Mayer celebrate animals that have traveled in space.
- The far-distant alien planet Beta Pictoris b – about 63 light years from Earth – pops right out in a picture by the Gemini Planet Imager. That’s a planet, orbiting a star over 600 trillion kilometers away! And now, getting a picture of it is easy.
Photo processing by Christian Marois, NRC Canada
- A thin ring of dust circles the star HR4796A, debris left over from the formation of the system.
- GPI can look at worlds in our solar system, too, like Jupiter’s moon Europa (right). Compare that to the map of the moon made by space probes that actually went there (left) [and you’ll see how faithful the GPI is to what’s actually there]. Photo by Marshall Perrin, Space Telescope Science Institute and Franck Marchis SETI Institute
TO EXPLORE STRANGE NEW WORLDS:
The Gemini Planet Imager Is Ready!
Condensed from a post by Phil Plait | Bad Astronomy - Slate
7 January 2014 || Stardate 67483.9
Get ready to see a lot of exoplanets images pretty soon: The Gemini Planet Imager is online and ready to seek out strange new worlds.
The Gemini Planet Imager, or GPI, is a camera that is used on the Gemini South telescope, an 8.1-meter behemoth located in Chile. GPI is the size of a small car and uses advanced optical techniques to provide incredibly crisp images of young planets orbiting distant suns.
It will be able to clearly see exoplanets even when they are 10 million times fainter than their parent stars, and separated by as little as 0.2 arcseconds: Roughly the apparent size of a quarter 25 kilometers (16 miles) away!
The camera is designed to look in the infrared [and thus see hot] young planets (less than a billion years old). It can also detect polarized light [such as the] light scattered off dust in space.
Read the full post: New camera to photograph alien worlds …
Help decide the future of human spaceflight with #HumansInSpace on Twitter today!
The National Academy of Sciences is using Twitter for the first time as *direct input* to a study on the future of human spaceflight. Any tweets made on October 29 with the hashtag #HumansInSpace will be accepted.
I would love to have everyone who follows this Tumblr tweet an idea or two - no need to be an expert at all - it’s open to everyone!
Neptune and Triton