OrbitalHub

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.

Credits: NASA GSFC

The solar wind generated by our Sun carves out a protective bubble around the solar system, called the heliosphere. The interstellar medium, consisting of the gas and the dust found between the galaxies, interacts with the solar wind and defines the actual boundary, which is called the termination shock.

NASA has designed a mission to map the boundary of the solar system. The mission is called IBEX (Interstellar Boundary Explorer) and it is ready to launch. The data collected by IBEX will allow scientists to understand the interaction between our Sun and the galaxy for the first time. Understanding this interaction will help us protect future astronauts from the danger of galactic cosmic rays.

In January 2005, the Orbital Science Corporation was selected to develop, build, and launch a small spacecraft for NASA’s IBEX mission. The IBEX spacecraft is based on an already existing bus: the MicroStar satellite. IBEX will be launched by a Pegasus XL rocket, which will be dropped from an aircraft flying over the Pacific Ocean.

Credits: NASA GSFC

Pegasus began its commercial career in April 1990, and since then it has launched more than 80 satellites into space.

Pegasus is a three-stage launching system used to deploy small satellites weighing up to 1,000 pounds into Low Earth Orbit (LEO). An aircraft carries Pegasus to an altitude of 40,000 feet.

The rocket is released and free-falls before igniting its engines. It takes roughly ten minutes for Pegasus to deliver a satellite into orbit.

Pegasus will place IBEX into a 130 mile altitude orbit. An extra solid-fueled rocket will boost the spacecraft from the LEO. IBEX’s final orbit will be a highly elliptical orbit with the perigee at an altitude of 7,000 km and the apogee at 236,000 km. IBEX has to operate in this orbit because any interference from the Earth’s magnetosphere would make it impossible to take accurate measurements with the scientific instruments onboard.

Credits: NASA GSFC

IBEX has a mass of only 83.33 lbs (roughly 38 kg) and is described by NASA as being the size of a bus tire. The instruments onboard IBEX will collect particles called energetic neutral atoms (ENAs). The ENAs are radiated from the termination shock region. The ENA hits recorded by the instruments onboard IBEX will be used to create a map of this region.

The mission is scheduled to launch tomorrow, October 19th, 2008. The spacecraft will be operational for 24 months. You can find out more about the IBEX spacecraft on NASA’s IBEX mission web page.

Credits: NASA

In the previous two posts in this series, we presented NASA’s Lunar Reconnaissance Orbiter (LRO) and the Chandrayaan-1 mission, which was designed and developed by ISRO. These two missions are typical lunar scouting missions: the spacecraft with onboard remote-sensing instruments will orbit the Moon, collect scientific data, and relay it back to Earth.

NASA will launch another lunar scouting spacecraft on the same Atlas V rocket with LRO: the Lunar Crater Observation and Sensing Satellite (LCROSS). This mission is not a typical scouting mission and we will see why in this post.

In 1999, a precursor of LRO and LCROSS called the Lunar Prospector detected traces of concentrated hydrogen at the lunar poles. As a result, the LCROSS mission’s main goal is to confirm the presence or absence of water in a permanently shadowed crater near a lunar polar region. At the present time, landing a probe on the lunar surface and performing excavations or drilling would be very expensive. A less expensive solution for the LCROSS mission is to use a kinetic impactor to excavate a crater on the surface of the Moon.

Credits: NASA

After the launch, LRO will separate from LCROSS, and continue on a solo journey to the Moon. LCROSS will remain attached to the Centaur upper stage of the Atlas V launch system.

While LRO will follow a trajectory that will place it in a polar lunar orbit, LCROSS will execute a flyby of the Moon, and use an elongated Earth orbit to position itself on an impact trajectory. During this time, the LCROSS mission team will perform instrument calibration and corrections for the impact trajectory. The target of the impact will be the lunar south pole.

Seven minutes before the impact, LCROSS will separate from Centaur. The Centaur will be used as a kinetic impactor. Having a mass of approximately 2,200 kg, on impact, it will excavate a crater 20 meters wide and 3 meters deep. According to NASA scientists, more than 250 tons of lunar material will be propelled into space.

Credits: NASA

LCROSS will then fly through the debris of the previous impact. The instruments onboard LCROSS will collect scientific data and the spacecraft will relay it back to Earth. LCROSS will end its mission four minutes after the Centaur impact by creating its own impact crater on the lunar surface. The last S in LCROSS should stand for Smasher instead of Satellite considering the final act of the mission!

The scientific instruments onboard LCROSS cover a wide spectrum: two near-infrared spectrometers, a visible light spectrometer, two mid-infrared cameras, two near-infrared cameras, a visible camera, and a visible radiometer. The instruments can detect traces of organics, hydrocarbons, hydrated minerals, water ice, and water vapor. More details about the LCROSS scientific payload can be found on LCROSS mission page.

I wonder to what extent the debris caused by the impact of Centaur and LCROSS will interfere with the scientific instruments onboard LRO and Chandrayaan-1. Both LRO and Chandrayaan-1 will be orbiting the Moon on polar orbits at that time.