OrbitalHub

Credits: ESA/AOES Medialab

In a previous post, we presented the Planck spacecraft. We would like to dedicate this post to Planck’s big brother, Herschel. Why b(r)other? Because Planck and Herschel will be launched into space by the same Ariane 5 launcher and they will share the fairing section during the launch phase of the mission. Why big? Well, because Herschel is a larger spacecraft than Planck… actually Herschel is the largest space telescope ever built.

Just to have an idea about the size of the infrared telescope onboard the Herschel spacecraft, the primary mirror has a diameter of 3.5 m and a mass of only 350 kg. In comparison, the mirror of the Hubble space telescope has a diameter of 2.4 m and a mass of 1.5 tons. Obviously, a great deal of effort has been put into minimizing the mass of the telescope, an advance made possible by present-day technology.

The infrared telescope will become operational four months after its launch and will have a nominal mission lifetime of three years. The objectives that ESA set for the Herschel Space Observatory are ambitious: the study of the galaxies in the early universe, the investigation of the creation of stars, the observation of the chemical composition of the atmosphere and surfaces of comets, planets and satellites, as well as examining the molecular chemistry of the universe.

Like Planck, Herschel will observe the sky from the second Lagrangean Point (L2) of the Sun-Earth system. The instruments onboard Herschel will collect long-wavelength infrared radiation. Herschel will be the only space observatory to cover the spectral range from the far infrared to sub-millimeter, which is the reason why the initial name of the space observatory was Far Infrared and Sub-millimeter Telescope (FIRST).

Credits: ESA

The Herschel spacecraft will have 3.3 tons at launch, with a length of 7.5 m and a cross section of 4×4 m. The spacecraft comprises of two modules: the service module and the payload module. While the service module contains the systems for power conditioning, attitude control, data handling and communications, and the warm parts of the scientific instruments, the payload module contains the telescope, the optical bench, the cold parts of the scientific instruments and the cooling system. A sunshield protects the telescope and the cryostat from solar radiation. The sunshield also carries solar cells for power generation.

In order to make accurate observations of the infrared spectrum, parts of the scientific instruments onboard have to be cooled to temperatures close to absolute zero. Two thousand liters of liquid helium will be used for primary cooling during the mission. In addition, each detector onboard is equipped with additional cooling systems.

Credits: ESA/Guarniero

Herschel will not be the first infrared telescope launched into space. There are three predecessors that we would like to mention here: IRAS, the US-Dutch-British satellite launched in 1983, ISO – launched by ESA in 1995, and the NASA’s Spitzer Space Telescope – launched in 2003. However, these three infrared space telescopes were operated on Earth orbits. As we mentioned, Herschel will operate in the L2 point, away from any interference that would affect the scientific instruments onboard. Operating in the L2 point will also help with regard to thermal stability because the spacecraft will not move in and out of eclipse regions.

The launch date is set for early 2009. The journey to the final operational position will take around four months. The European Space Operations Control Center (ESOC) in Darmstadt will coordinate the mission.

Credits: ESA

This week, the Carnival of Space is hosted in Sweden at As(si)tronomi by Assi Süer. This is the 76th edition of the Carnival.

OrbitalHub submitted a story about the XMM-Newton space telescope.

There are two updates that we would like to bring to your attention. The first is that ESA re-established radio contact with XMM-Newton. Also, the GOCE mission is postponed until February 2009 due to technical problems with the upper stage of the launch vehicle.

Credits: CNES / D. Ducros

Stellar seismology is a relatively new field of study. Since 1995, the ESA/NASA mission SOHO (SOlar Heliospheric Observatory) has pioneered the study of stellar seismology through observations of our own star, the Sun. Despite its name, stellar seismology is the study of stellar pressure waves and not stellar seismic activity (There is no such thing as seismic activity inside a star).

The COROT mission uses a similar approach to study other stars. Three stars similar to the Sun – known as HD499933, HD181420, and HD181906 – have been probed and starquakes have been detected.

Credits: CNES

Starquakes, or oscillations of distant stars, can be detected through variation in the light emitted by the star as sound waves hit the star’s surface.

This method reveals the internal structure of the star, and the patterns that the energy follows when transported from the core to the surface. These observations also allow astronomers to calculate the star’s mass, age, and chemical composition.

The COROT satellite, carrying a 27 cm diameter telescope, was launched in December 2006 by a Soyuz rocket from the Baikonur Cosmodrome. COROT is a 360 kg satellite and operates on a polar orbit at an altitude of 896 km. COROT is a mission lead by the French Space Agency (CNES); ESA, Austria, Belgium, Germany, Spain, and Brazil also contributed to the mission. The main objectives of the mission are to search for exoplanets and to study stellar interiors.

Credits: CNES

The telescope onboard COROT cannot see exoplanets directly. The method employed by COROT to discover exoplanets is to measure variations in the luminosity of stars. Planets cause such variations as they pass in front of their parent stars. These celestial alignments are called planetary transits. Obviously, the smaller the planet, the higher the telescope’s sensitivity must be in order to detect it.

Ground telescopes have detected more than 200 exoplanets to date (all of them gas giants). COROT continues the search for new worlds outside of our solar system from above the Earth’s atmosphere. Without the distorting effects of the atmosphere, COROT is able to find planets that are made out of rock and are smaller than the gas giants. COROT marks the first step in understanding other solar systems, how planets are formed, and how life can develop on these planets.

From February 2 to February 5, 2009, the first COROT International Symposium will be held in Paris, France.

Credits: ESA

After operating flawlessly in orbit for almost nine years, the XMM-Newton X-ray observatory lost contact with the ESA’s ground stations.

In the case of a space mission, losing contact with a spacecraft can mean anything from a technical problem onboard to a collision with space debris or even a meteorite.

The contact was lost when the satellite switched from one ground station to another. The satellite must perform such operations in orbit in order to maintain radio contact with the ground control center of the mission. The ESA’s ground station in Villafranca, Spain, reported that it was not able to re-establish radio contact with the satellite.

Several astronomic observatories have managed to take images of the satellite in orbit. By now it is clear to the ground investigators that the satellite is intact and it is maintaining a constant altitude on the expected orbit. By using a more powerful ground antenna (the 35m diameter antenna at New Norcia in Australia), a weak radio transmission was received from XMM-Newton, proving that the satellite is still alive. Engineers hope to re-establish nominal radio contact with the satellite.

Credits: NASA/ESA/R. Massey (Caltech)

ESA launched the X-ray Multi-Mirror Mission (XMM-Newton) on December 10th, 1999. The mission has an operational lifetime of ten years. XMM-Newton has a large collecting area due to its three X-ray telescopes. In addition, the high altitude orbit offers the ability to make long uninterrupted exposures.

X-rays are absorbed by the Earth’s atmosphere, so only a space telescope like XMM-Newton can detect and study celestial X-ray sources.

Data collected by the XMM-Newton was used to compile a three-dimensional large-scale map of the dark matter for the first time. The dark matter is an invisible form of matter that accounts for most of the mass of the Universe.

ESA has an entire website dedicated to the XMM-Newton mission. For more details about XMM-Newton you can visit the XMM-Newton Science Operations Center (XMM-Newton SOC) page.

Courtesy of JAXA/NHK

On September 14th, 2007, the Japan Aerospace Exploration Agency (JAXA) launched the second Japanese lunar explorer, Kaguya. Kaguya was launched by an H-IIA Launch Vehicle from the Tanegashima Space Center (Mitsubishi Heavy Industries, Ltd. has a special page dedicated to the H-IIA No. 13, which was the rocket used for the Kaguya mission).

Kaguya shared the journey to the Moon with two smaller satellites, Okina and Okuna. Once in lunar orbit, Kaguya released the small satellites on elliptical orbits around the Moon. Okina and Okuna play the role of orbiting radio transmitters, relaying the data from Kaguya back to Earth in real time when Kaguya is above the far side of the Moon.

Courtesy of JAXA/NHK

The instruments onboard the spacecraft have measured the composition and the topography of the lunar surface for more than one year.

Mapping of the lunar magnetic field was also performed.

The NHK HDTV cameras on Kaguya recorded stunning movies of the Earth rising and setting over the lunar surface. The movies are now available on JAXA’s web site.

Credits: ESA

The Carnival of Space #75 is hosted this week at the Lounge of the Lab Lemming.

OrbitalHub is hosted under the second carnival tent and is presenting ESA’s GOCE spacecraft. We hope you will enjoy reading our submission to this week’s space carnival.