ESA: ERS satellite missions complete after 20 years

The second European Remote Sensing satellite, ERS-2, was shut down on 5 September 2011. ERS-2 travelled 3.8 billion km during its lifetime, providing data for thousands of scientists and projects.

Credits: ESA

After a final thruster firing last week to deplete its remaining fuel, ESA's venerable ERS-2 observation satellite has been safely taken out of service.

Ground controllers also ensured the space environment was protected for future missions.

The mission ended on 5 September, after the satellite's average altitude had already been lowered from 785 km to about 573 km. At this height, the risk of collision with other satellites or space debris is greatly reduced.

The final critical step was to 'passivate' ERS-2, ensuring that all batteries and pressurised systems were emptied or rendered safe in order to avoid any future explosion that could create new space debris.

This primarily consisted of burning off the fuel, disconnecting the batteries and switching off the transmitters.

"As soon as we saw fuel depletion occurring, a series of commands was sent to complete passivation, before shutting the satellite down for good. The last command was sent at 13:16 GMT on 5 September," said Frank Diekmann, ERS-2 Operations Manager.


Atmospheric burn up

With the effects of natural atmospheric drag, ERS-2 is predicted to enter and largely burn up in the atmosphere in about 15 years. This is well within the 25-year-limit that is imposed to minimise the risk of collision before re-entry.

"ERS-2 deorbiting is being conducted in compliance with ESA's space debris mitigation requirements," said Heiner Klinkrad, Head of ESA’s Space Debris Office.

"This indicates the strong commitment by the Agency to reducing space debris, which can threaten current and future robotic and human missions."

Electric sense in dolphins: cetaceans with a seventh sense

One extra sense isn't quite enough for Guiana dolphins. In addition to echolocation, they can sense the electric fields of their prey – the first time this has been seen in true mammals.

Wolf Hanke at the University of Rostock in Germany and colleagues were intrigued by thermal images showing intense physiological activity in the pits on the upper jaw of the dolphins, Sotalia guianensis. 

Fish, some amphibians and primitive egg-laying mammals such as the duck-billed platypus use similar pits to pick up electric fields generated by nearby animals.

By examining the structures in a dead dolphin, and training a live one to respond to an electric field comparable to that generated by a fish, the team showed that dolphins also have electro-sensory perception.

"Electroreception is good for sensing prey over short distances, where echolocation isn't so effective," says Hanke. Other species of dolphin, and even whales, may be similarly gifted, he says.

"Most people don't realise that whales also feed on the floor of the ocean, so it is possible that they also use electrosensing."

Hanke points out that the electro-sensory organs are derived from whiskers in ancestral animals. These mechanoreceptor organs, like the hair cells in the human ear, mechanically transmit the stimulus of touch or sound waves. 

The adaptation in Guiana dolphins is fairly new, Hanke says, and he suspects that "it is relatively easy to evolve, to change mechanoreceptor organs into electroreceptors".

Indeed, the finding suggests nearly all mammals have at least the potential to evolve it too.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2011.1127

Feel Space Project at University of Osnabruck

At the University of Osnabruck in Germany, a group of scientists have been developing the remarkable 'feel-space' belt which allows the wearer to feel the earth's magnetic field, just like birds do.

The feelSpace belt has vibrators attached, which are governed by heading information from an electronic compass: the one vibrator pointing north is active.

Thereby, the belt user is constantly provided with tactile heading information relative to the earth's magnetic field. If, for instance, the user is directed to west, the vibrator on his right hip vibrates.

For six weird weeks twelve volunteers wore the vibrating sensory belt every moment of their waking day and sure enough at the end of their trial all the evidence suggests that they managed to incorporate their new sense, navigating their way around the world instinctively by-passing the need for attention altogether.

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Blind Boy Using Echo Location to Aid his Senses

Blind seven-year-old Lucas Murray is making the headlines today with his supposed ability to "see" using his ears. He is in fact using sound as a location aid.

Lucas, who has become one of the first in the UK to learn the technique and of course, he has been nicknamed 'batboy', by the Press, after learning how to use echoes to picture the world around him.

He clicks his tongue on the roof of his mouth and the sound that comes back tells him the distance, shape, density and position of objects.

Lucas, from Poole in Dorset, who was born blind, can even shoot basketball hoops, rock climb and run around the playground with the technique which is similar to that used by other sound sensitive mammals; bats, dolphins, etc.

He tells distance by timing how long the echo takes to return, the ear the sound reaches first tells him location and he picks up the density and shape of an object by the intensity of the sound bouncing back. An object moving away creates a lower pitch and vice versa.

Lucas was taught by Californian Daniel Kish, 43, who is himself blind and in his efforts to improve the lives of other blind people, he has founded the World Access for the Blind charity.