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 NASA examines Peru's deadly rainfall
24.03.2017 | NASA/Goddard Space Flight Center

nachricht Steep rise of the Bernese Alps
24.03.2017 | Universität Bern

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>