OrbitalHub

Credits: ESA/CNES/Arianespace РOptique vid̩o du CSG, L. Boyer

Arianespace was founded in 1980. With twenty-four shareholders from ten European countries (among which CNES holds 34% and EADS 30%), Arianespace is the world’s first commercial space transportation company.

The workhorse of Arianespace has been the Ariane launch vehicle.

Five versions of Ariane have served the company so far: Ariane 1, with the first successful launch on December 24, 1979, Ariane 2, launched for the first time on November 20, 1987, Ariane 3, starting its service on August 4, 1984, Ariane 4, launched on June 15, 1988, and Ariane 5, with the first successful flight on October 30, 1997.

The first launch of Ariane 5, a.k.a. Flight 501, ended with the vehicle being destroyed by its automated self-destruct system, after the high accelerations caused the inertial guidance system to crash. The crash was caused by, I quote, one of the most infamous computer bugs in history. If you like, you can take a look at the Ada code that caused the malfunction. But enough with the dark memories, this is an anniversary after all…

Since its inception, Arianespace has signed over 300 contracts that resulted in more than 277 satellite launches. According to Arianespace, Ariane launchers have delivered more than half of all commercial satellites now in service. The year 2009 was a very successful year for Ariane 5. The launcher orbited nine commercial satellites, the Herschel space telescope, the Planck scientific observatory, and the Helios 2B observation satellite. Ariane 5 has proven to be a versatile launch vehicle, capable of handling a wide range of missions.

The challenges for 2010 are many, as Arianespace is planning up to seven Ariane 5 launches. Two new launch vehicles will join Ariane 5 as part of the Arianespace family of launchers: the Vega small launcher and the Soyuz medium launcher.

You can read more about Arianespace, its mission, and the solutions provided to customers around the world on the Arianespace website.

Credits: ESA – D. Ducros, 2009

While the media has been busy with the launch of the STS-125 Atlantis for the Hubble Servicing Mission #4 from Cape Canaveral, another exciting launch is undergoing preparations further south, in Kourou, French Guiana.

Herschel and Planck are scheduled to launch on May 14, 2009. They will be stacked on the same Ariane 5 launch vehicle.

The two spacecraft will separate shortly after the launch (Herschel a couple of minutes before Planck) and will proceed independently to the L2 point of the Sun-Earth system. L2 is a point in space that has some special characteristics situated at 1.5 million kilometers from Earth in the opposite direction to the Sun. Herschel and Planck will operate from independent orbits around the L2 point.

Credits: ESA – D. Ducros, 2009

Stacked together, Herschel and Planck measure around 11 m in length, 4.5 m in diameter, and have a mass of approximately 5,700 kg. The piece that holds them together is called Sylda. Sylda is a support structure for Herschel and forms a protective cover for Planck.

The final orbit for Herschel will be a large, 900×500-thousand km, Lissajous orbit around the L2. There are three trajectory-correction maneuvers (TCM) planned for Herschel, during days L+1, L+2, and L+12. Planck will require a total of 5 TCMs that will enable it to operate from a 300×200-thousand km Lissajous orbit also around the L2 point.

The Lissajou orbits are inherently unstable, so both spacecraft will need regular thruster burns throughout their missions to stay on track.

“Without regular trajectory corrections, they would naturally drift off into a useless orbit about the Sun or Earth, with the rate of drift increasing with time,” says Gottlob Gienger, the senior flight dynamics advisor for the Herschel and Planck missions.

To read more about the launch of Herschel and Planck, you can visit the dedicated page on ESA’s website.

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.