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Odin photo album

ODIN, the Swedish space observatory

The Odin satellite was designed and developed by SSC on behalf of the Swedish National Space Board and the space agencies of Canada, Finland and France. The satellite, operated by SSC, was launched in February 2001 on a Start-1 launch vehicle from Svobodny. Odin required a 2-year lifetime but is still fully operational into its 7th year and Odin is still delivering valuable data to the scientists. Odin was the fifth scientific research satellite to be developed in Sweden.

How are stars born and solar systems developed? How did our own planet come into existence? What is happening to the ozone layer in the atmosphere and to our climate? The Norse god Odin is said to have sacrificed one of his eyes at the well of the giant Mimer in order to gain universal wisdom. The science satellite Odin provides us with knowledge, and like the ancient divinity the orbital observatory has one all-viewing eye – a sensitive radio telescope. Aimed at both heaven and Earth, the Odin eye helps us to better understand the history of the universe and to control our own future.

Odin combines two scientific disciplines on a single spacecraft for studies of star formation (astronomy) and of the mechanisms behind the depletion of the ozone layer in the Earth atmosphere (aeronomy). These complex missions require highly accurate pointing, for aeronomy the spacecraft follows the Earth limb – scanning the atmosphere up and down from 15 to 120 km at a rate of up to 40 scans per orbit. When observing astronomical sources Odin is continuously pointing towards the object for up to 60 minutes.

The double mission of Odin

Star formation
Solar systems with planets are formed when giant clouds of dust and gas collapse from their internal gravity. This happened also when our solar system, including our own planet Tellus, was formed. The clouds consist of a mixture of elements from the early universe and remnants from old stars. In the process, the molecules of the gas emit excess energy in long wavelengths cooling the cloud so that it can continue collapsing until, finally, the star is lit. These clouds exist both in our Milky Way and in other galaxies. Odin studies the composition of the clouds – in particular how much water and oxygen they contain. By aiming the telescope also at comets and giant planets we gain knowledge about the birth of our own solar system.

The ozone holes
The ozone layer, at 25-40 km altitude, is formed when molecular oxygen (O2) is broken up into atoms by the rays of the sun, atoms which then recombine with molecular oxygen to form ozone (O3). The ozone gas works as a filter against the ultraviolet radiation from the sun. A depleted ozone layer results in more harmful UV radiation reaching the surface of Earth. For humans this means an increased risk for skin cancer. Man has released chlorine compounds like freons into the atmosphere, which break up the ozone and make the gaseous layer thinner. In this way the Antarctic ozone hole is formed. Even in our latitudes the ozone layer is affected. Odin investigates how the chlorine compounds influence the ozone depletion. It will enable the scientists to tell if the reduction of freon release undertaken by many countries has had a positive effect on the ozone layer.

How the eye of Odin works
The eye of Odin is a radio telescope working in principle like an ordinary radio receiver. But instead of broadcasts from a radio station, Odin receives signals from different molecules in space and in the atmosphere. The signals from these substances are at frequencies 5000 times higher than those from an FM- band radio station. Each molecule emits signals and the more molecules there are the stronger the signal will be. In this way the scientists will find out how much of various gases there are in the direction Odin is looking, for instance how much chlorine from freons there are at different altitudes in the atmosphere. The gases of highest interest to the atmospheric scientists are chlorine monoxide and ozone. The astronomers focus on water vapour and oxygen. Since the signals to be measured are weak, they are lost in the thick atmosphere close to the Earth surface and can therefore be measured only from space.

A radiometer, designed and developed by SSC, is the primary payload. It features a 1.1 m telescope of high surface accuracy and actively cooled receivers, four at the previously unexplored wavelenght region around 500 GHz and one at 119 GHz.

The radiometer package has one receiver at a wavelength of 3 mm and four in the submm band (l ~ 0.5 mm). Type Single side band heterodyne receivers

• Frequencies 118.25 – 119.25 GHz, 486.1 – 503.9 GHz, 541.0 – 580.4 GHz
• Bandwidth 100 MHz to 1 GHz
• Resolution 0.1 MHz to 1 MHz
• Sensitivity 1 K in 1MHz with S/N=5 after 15 min
• Mixers Cooled Schottky mixers
• LO Local oscillators based on Gunn diodes and frequency multipliers
• LNA Cooled HEMT low noise amplifiers
• Spectrometer hybrid autocorrelator and AOS

Odin also carries an optical spectrograph, OSIRIS. This instrument has four wavelength bands, from UV to IR and views the limb through optics separate but aligned with the submm antenna.

• Type Grating spectrometers
• Wavelengths 280 – 800 nm and 1270 nm
• Resolution Optical: 1 nm, IR: 10 nm
• Aperture 10 cm2
• FOV 0.02° x 0.75°.

Technical characteristics:

• Platform: 3-axis stabilized with reaction wheels, star trackers and gyros
• Mass: 250 kg (170 kg bus and 80 kg payload)
• Size Height: 2.0 m, width: 1.1 m stored and 3.8 m in operational state
• Power: 340 W from deployable fixed arrays
• Cooling Closed Stirling cycle coolers
• Pointing: ±15 arcsec in staring mode ±1.2 arcmin scanning (reconstructed)
• Datalink: > 720 kbit/s to Esrange tracking station
• Storage: >100 Mbyte in solid state memory
• Launched February 20, 2001 on a Start-1 launch vehicle from Svobodny
• Orbit Circular sunsynchronous, 600 km altitude with ascending node at 18:00
• Design lifetime: 2 years minimum
• Odin is in a 600-km altitude orbit with 15 revolutions per day around the Earth
• Odin is the only satellite, world-wide, to have continuously measured the chlorine
  chemistry in the ozone layer since 2001.
• Odin data are received by the SSC ground station at Esrange.

Read more about Odin on the Odin results page.

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