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First year-long stay on the ISS about to begin

Posted 26/03/2015

Two astronauts are set to get extra comfy on the International Space Station when they launch on Friday for the ISS's first ever year-long mission, double the length of the normal stay. The mission will help the US and Russia study the long-term effects of space flight, which is essential if humans are ever to fly to Mars.


NASA's Scott Kelly will join Mikhail Kornienko and Gennady Padalka, from Russia's space agency Roscosmos, on a Soyuz spacecraft due to launch on 28 March from Baikonur Cosmodrome in Kazakhstan. Kelly and Kornienko will spend a year on the station.

Serendipitously, Kelly has an identical twin brother, Mark, who is also an astronaut but will spend this year on the ground. NASA will compare data on the twins' health to try to distinguish the effects of space flight from those of genetics.

Thanks to Einstein's theory of relativity, which says a traveller in a fast-moving spacecraft ages less than someone on Earth, Scott Kelly will return about 10 milliseconds younger than Mark at the end of the year – although the difference is too small to measure.

Kelly and Kornienko won't beat the record for the longest single space flight. That is held by Valeri Polyakov, who spent nearly 440 days on board the Mir space station in the 1990s. But researchers studying the astronauts will make use of modern techniques such as microbiome analysis that weren't available during Polyakov's flight. After the US Space Shuttle program ended in 2011, Soyuz rockets became the only provider of transport for astronauts at the International Space Station, and Dragon became the only provider of bulk cargo-return-to-Earth services (downmass capability of Soyuz capsules is very limited).

The ISS programme is a joint project among five participating space agencies: NASA, Roscosmos, JAXA, ESA, and CSA.

The ownership and use of the space station is established by intergovernmental treaties and agreements. Roscosmos logoRoscosmos logoThe station is divided into two sections, the Russian Orbital Segment (ROS) and the United States Orbital Segment (USOS), which is shared by many nations. As of January 2014, the American portion of ISS was funded until 2024. Roscosmos has endorsed the continued operation of ISS through 2024, but have proposed using elements of the Russian Orbital Segment to construct a new Russian space station called OPSEK.

The ISS serves as a microgravity and space environment research laboratory in which crew members conduct experiments in biology, human biology, physics, astronomy, meteorology and other fields.The station is suited for the testing of spacecraft systems and equipment required for missions to the Moon and Mars. The ISS maintains an orbit with an altitude of between 330 and 435 km (205 and 270 mi) by means of re-boost manoeuvres using the engines of the Zvezda module or visiting spacecraft. It completes 15.54 earth orbits per day.



Lots of light and little shadow on 67P Churyumov-Gerasimenko

Posted 08/03/2015

On 14 February 2015, the Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS) on the Rosetta spacecraft observed the surface of comet 67P Churyumov-Gerasimenko with the Sun directly behind it, so the only shadow seen in the image is that of the photographer, the orbiter itself.

"An image with this arrangement of the light source and camera really reveals the differences in brightness on the comet's surface. As there are no shadows, this difference must be due to the scattering of the light by the dust particles across the comet's surface," explains Ekkehard Kührt, a cometary researcher at the German Aerospace Centre (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and a scientist on the OSIRIS team.

"This means, for instance, that it is possible to calculate the sizes of the dust particles spread across the surface, even though these are far below the camera's resolution threshold." 

Overflight view of comet 67P Churyumov-Gerasimenko. The image was acquired as the orbiter passed over the comet at an altitude of just six kilometres.

Smooth plains and rugged areas

Measuring 228 by 228 metres, the terrain shows abruptly terraced steps separating flat ground from fissured areas. The camera system is looking straight down from above, which makes estimating the actual height of the terraces quite difficult.

Scientists have given this region, which is situated not far from the equator of the larger part of the comet nucleus, the name Imhotep.

Unfortunately, it is on the opposite side to Philae's landing site, which means the scientists were denied the possibility of discovering the landing craft's location during this overflight. Rosetta's shadow is visible as a dark patch in the lower half of the image. The adjacent surface of the comet is brighter than the rest, as here the comet, the orbiter and the Sun are aligned precisely along the same axis. 

The low-altitude overflight of 67P Churyumov-Gerasimenko did not last long; by 17 February 2015, the Rosetta orbiter had already reached a distance of 253 kilometres from the comet, before returning to within 76 kilometres on 25 February. It re-examined the surface from an altitude of 110 kilometres on 28 February.

Up close to the comet

The OSIRIS image of 14 February – the day the orbiter came closest to the comet – has a resolution of 11 centimetres per pixel. So far, only the Rosetta Lander Imaging System (ROLIS), installed on the bottom of the Philae lander, has been able to acquire higher resolution photographs of the comet's surface, taking images at a resolution of four centimetres per pixel as it descended towards 67P Churyumov-Gerasimenko.

Scientists are currently analysing photographs of the comet's surface, which were taken immediately after landing using artificial light. It is hoped that these images, which have a resolution of less than one millimetre per pixel, will provide definitive information on the celestial body’s fine structure. Preliminary results are expected in April 2015. 

The mission

Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is funded by a consortium headed by DLR, the Max Planck Institute for Solar System Research (MPS), CNES and the Italian Space Agency (ASI).

The OSIRIS camera was built by a consortium led by the Max Planck Institute for Solar System Research (Germany), in collaboration with the Center of Studies and Activities for Space (CISAS) at the University of Padua (Italy), the Laboratoire d'Astrophysique de Marseille (France), the Institute of Astrophysics of Andalusia (IAA-CSIC) (Spain), ESA's Scientific Support Office, the National Institute for Aerospace Technology (Instituto Nacional de Técnica Aeroespacial) (Spain), the Technical University of Madrid (Universidad Politécnica de Madrid) (Spain), the Department of Physics and Astronomy at Uppsala University (Sweden), and the Institute of Computer and Network Engineering at the Braunschweig University of Technology (Germany). OSIRIS was funded by national agencies in Germany (DLR), France (CNES), Italy (ASI), Spain (MEC) and Sweden (SNSB), as well as ESA's Technical Directorate.

The shadow seen on the comet’s surface is Rosetta’s penumbra. Such penumbras occur when an object is illuminated by an extended light source like the Sun.