Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Micro-satellite steers by the stars to return views of Earth

01.06.2004


HRC image was acquired 24 April 2004 and shows Uluru, also known as Ayers Rock. It is the world’s largest monolith, and a sacred site to Australia’s Aborigines. It is 3.6 km long and two km wide. The walk around it covers 9.4 km.
Credits: ESA


Since its launch in October 2001, ESA’s Proba micro-satellite has been returning remarkable imagery of some of our planet’s major landmarks with a compact instrument called the High Resolution Camera.

On display here are some notable examples, ranging from the monolithic Uluru or Ayers Rock in the Australian Outback to the tidal island of Mont St. Michel on the northern coast of France, and the Pyramids on Egypt’s Giza Plain.

Measuring just 80 x 60 x 60 cm, Proba is the size and shape of a small washing machine. It orbits 600 km above the Earth’s surface.


Its main payload is the Compact High Resolution Imaging Spectrometer (CHRIS), a compact hyperspectral imager that returns detailed data on the Earth’s environment, seeing down to a resolution of 18 metres.

Also aboard is the compact High-Resolution Camera (HRC), which acquires black and white 25-km square images to a resolution of five metres.

Proba was originally created as a technology demonstration mission, and has a high degree of onboard autonomy.

Operators on the ground send up the raw inputs of a target to be imaged – latitude, longitude, and altitude – and Proba itself does the rest.

Proba keeps track of its orbital position with a Global Positioning System (GPS) receiver.

This works on the same basic principle as GPS navigation systems in wide use down on our planet’s surface.

However because Proba is travelling at a very high velocity in relation to the GPS satellite constellation the receiver has been designed to cope with much higher rates of Doppler shifting as well as the constant changing of the individual GPS satellites being tracked.

To image a target on the ground, Proba must be correctly lined up with it. To precisely determine its attitude (or pointing direction) in space, the satellite supplements GPS with an onboard star tracker system called the Advanced Stellar Compass (ASC).

The ASC compares observed luminous objects to a star catalogue database containing thousands of stars in order to accurately calculate its orientation in relation to its desired target.

Proba then adjusts its position to line itself up with its ground target by use of reaction wheels capable of a high level of precision control: increasing the rate a wheel spins causes the spacecraft to rotate in the opposite direction, then braking by the same amount cancels out this rotation.

During the actual imaging procedure Proba employs its reaction wheels to compensate for natural orbital movement and keep itself ’staring’ at its target.

About Proba

Proba (Project for On Board Autonomy) is an ESA micro-satellite built by an industrial consortium led by the Belgian company Verhaert, launched from India on 22 October 2001, and operated from ESA’s Redu Ground Station in Belgium.

Proba was designed to be a one-year technology demonstration mission of the Agency but has since had its lifetime extended as an Earth Observation mission.

It now routinely provides scientists with detailed environmental images thanks to CHRIS, developed by UK-based Sira Electro-Optics Ltd - one of the main payloads on the 100 kg spacecraft.

Also aboard is the HRC, a small-scale monochromatic camera made up of a miniature Cassegrain telescope and a 1024 x 1024 pixel Charge-Coupled Device (CCD), as used in ordinary digital cameras.

Proba boasts an ’intelligent’ payload and has the ability to observe the same spot on Earth from a number of different angles and different combinations of optical and infra-red spectral bands.

A follow-on mission, Proba-2, is due to be deployed by ESA around 2005.

Mariangela D’Acunto | ESA
Further information:
http://www.esa.int/esaSA/SEMXW8HHZTD_earth_0.html

More articles from Earth Sciences:

nachricht Colorado River's connection with the ocean was a punctuated affair
16.11.2017 | University of Oregon

nachricht Researchers create largest, longest multiphysics earthquake simulation to date
14.11.2017 | Gauss Centre for Supercomputing

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>