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 Mineral discoveries in the Galapagos Islands pose a puzzle as to their formation and origin
19.10.2018 | Johannes Gutenberg-Universität Mainz

nachricht Massive organism is crashing on our watch
18.10.2018 | S.J. & Jessie E. Quinney College of Natural Resources, Utah State University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Goodbye, silicon? On the way to new electronic materials with metal-organic networks

Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz (Germany) together with scientists from Dresden, Leipzig, Sofia (Bulgaria) and Madrid (Spain) have now developed and characterized a novel, metal-organic material which displays electrical properties mimicking those of highly crystalline silicon. The material which can easily be fabricated at room temperature could serve as a replacement for expensive conventional inorganic materials used in optoelectronics.

Silicon, a so called semiconductor, is currently widely employed for the development of components such as solar cells, LEDs or computer chips. High purity...

Im Focus: Storage & Transport of highly volatile Gases made safer & cheaper by the use of “Kinetic Trapping"

Augsburg chemists present a new technology for compressing, storing and transporting highly volatile gases in porous frameworks/New prospects for gas-powered vehicles

Storage of highly volatile gases has always been a major technological challenge, not least for use in the automotive sector, for, for example, methane or...

Im Focus: Disrupting crystalline order to restore superfluidity

When we put water in a freezer, water molecules crystallize and form ice. This change from one phase of matter to another is called a phase transition. While this transition, and countless others that occur in nature, typically takes place at the same fixed conditions, such as the freezing point, one can ask how it can be influenced in a controlled way.

We are all familiar with such control of the freezing transition, as it is an essential ingredient in the art of making a sorbet or a slushy. To make a cold...

Im Focus: Micro energy harvesters for the Internet of Things

Fraunhofer IWS Dresden scientists print electronic layers with polymer ink

Thin organic layers provide machines and equipment with new functions. They enable, for example, tiny energy recuperators. In future, these will be installed...

Im Focus: Dynamik einzelner Proteine

Neue Messmethode erlaubt es Forschenden, die Bewegung von Molekülen lange und genau zu verfolgen

Das Zusammenspiel aus Struktur und Dynamik bestimmt die Funktion von Proteinen, den molekularen Werkzeugen der Zelle. Durch Fortschritte in der...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Conference to pave the way for new therapies

17.10.2018 | Event News

Berlin5GWeek: Private industrial networks and temporary 5G connectivity islands

16.10.2018 | Event News

5th International Conference on Cellular Materials (CellMAT), Scientific Programme online

02.10.2018 | Event News

 
Latest News

Nanocages in the lab and in the computer: how DNA-based dendrimers transport nanoparticles

19.10.2018 | Life Sciences

Thin films from Braunschweig on the way to Mercury

19.10.2018 | Physics and Astronomy

App-App-Hooray! - Innovative Kits for AR Applications

19.10.2018 | Trade Fair News

VideoLinks
Science & Research
Overview of more VideoLinks >>>