OrbitalHub

Credits: ESA

A Rockot launch vehicle lifted off from the Plesetsk Cosmodrome in northern Russia on November 2, 2009, at 02:50 CET. Rockot carried to orbit two new ESA satellites: SMOS and PROBA-2.

SMOS was released by the Breeze-KM upper stage some 70 minutes after the launch. After arriving at a lower orbit, the upper stage released Proba-2 around three hours after the launch.

The Soil Moisture and Ocean Salinity (SMOS) mission, which is the second Earth Explorer Opportunity mission to be developed as part of ESA’s Living Planet Program, will provide global maps of moisture over the Earth’s landmasses and salinity over the oceans. These observations will improve our understanding of hydrology and ocean circulation patterns.

PROBA-2 is part of an ESA program called In-Orbit Technology Demonstration Program, which is dedicated to the demonstration of innovative technologies. The PROBA-2 payload consists of scientific instruments that will make observations of the Sun in the ultraviolet portion of the spectrum and will measure certain properties of the plasma surrounding the spacecraft.

Credits: ESA – P. Carril, 2009

PROBA-2 is part of an ESA program called In-Orbit Technology Demonstration Program, which is dedicated to the demonstration of innovative technologies.

The PROBA-2 payload consists of scientific instruments that will make observations of the Sun in the ultraviolet portion of the spectrum and will measure certain properties of the plasma surrounding the spacecraft.

Among the new equipment and technologies demonstrated by PROBA-2 are new models of star trackers, GPS receivers, and reaction wheels, a new type of lithium-ion battery, an advanced data and power management system, composite carbon-fibre and aluminum structural panels, and magnetometers. PROBA-2 also hosts a digital Sun-sensor, an experimental solar panel, and a xenon gas propulsion system.

PROBA-2 will be launched onboard the same launch vehicle as SMOS. While the SMOS Mission will provide global maps of moisture over the Earth’s landmasses and salinity over the oceans, PROBA-2 is a small technology demonstrator. Launched as a secondary payload, PROBA-2 will orbit in the same plane as SMOS, but at a lower altitude. The planned mission duration is two years.

The spacecraft is a 600 mm x 700 mm x 850 mm box-shaped structure, with a mass of 130 kg. Aluminum honeycomb panels make the primary mechanical structure of the spacecraft. The two deployable solar panels and the one outer solar panel provide a maximum of 110 Watts of electrical power. A lithium-ion battery provides power during eclipse periods. A single 20 mN thruster is used for orbit adjustments.

Credits: ESA – P. Carril, 2009

PROBA-2 is three-axis stabilized. Attitude changes are performed using four reaction wheels that can be unloaded by magnetorquers, while the attitude determination is provided by star trackers, GPS sensors, and a three-axis magnetometer.

The spacecraft was built by Verhaert Design & Development NV, Belgium.

The scientific payload comprises of four experiments: two for solar observations (LYRA and SWAP) and two for space weather measurements (DSLP and TPMU).

LYRA is a Lyman-Alpha radiometer that will monitor four bands in a very wide ultraviolet spectrum. SWAP (the Sun Watcher using Active Pixel-sensor) will make measurements of the Sun’s corona. DSLP (Dual Segmented Langmuir Probes) will make measurements of the electron density and temperature in the background plasma. TPMU, which is the Thermal Plasma Measurement Unit, will measure ion densities and composition.

Launch services for the PROBA-2 mission are provided by EUROCKOT Launch Services GmbH. PROBA-2 will achieve its lower orbit by an orbit change maneuver of the Breeze-KM upper stage of the Rockot launch vehicle.

Credits: ESA – P. Carril, 2009

Rockot is a three-stage liquid propellant launch vehicle based on the Russian SS-19 Intercontinental Ballistic Missile (ICMB).

Rockot’s first and second stages (provided by SS-19) are completed by a third re-ignitable stage, the Breeze-KM upper stage. Rockot can deliver 1950 kg payloads to Low Earth Orbits (LEOs).

The length of the launch vehicle is 29 m. The external diameter of the stages is 2.5 m, while the payload fairing has an external diameter of 2.6 m and a height of 6.7 m. The mass of the vehicle at launch is 107 metric tons.

PROBA-2 will be carried into orbit from Plesetsk Cosmodrome, Russia. The operational orbit is a 700 km sun-synchronous orbit, with a 98 degree inclination.

You can read more about PROBA-2 on ESA’s dedicated web site. ESA’s web site also provides information about PROBA-1, which is already flying, and future PROBA missions, like PROBA-3 and PROBA-V.

Credits: ESA-AOES Medialab

The Soil Moisture and Ocean Salinity (SMOS) mission, which is the second Earth Explorer Opportunity mission to be developed as part of ESA’s Living Planet Program, will provide global maps of moisture over the Earth’s landmasses and salinity over the oceans. These observations will improve our understanding of hydrology and ocean circulation patterns.

The science objectives for the SMOS mission are global monitoring of surface soil moisture and surface salinity over oceans, and improving the characterization of ice and snow-covered surfaces.

The SMOS satellite is built around a standard spacecraft bus called Proteus, which was developed by the French space agency CNES (Centre National d’Etudes Spatiales) and Alcatel Alenia Space. Proteus measures one cubic meter and plays the role of a service module, hosting all the subsystems that are required for the satellite to function.

A GPS receiver collects satellite position information. A hydrazine monopropellant system consisting of four 1-Newton thrusters, which are mounted on the base of the spacecraft, provides the thrust for orbit control. Three 2-axis gyroscopes and four small reaction wheels control the attitude of the satellite. A star tracker also provides accurate attitude information for instrument measurements.

The solar panels can produce up to 900 W, covering the 525 W maximum payload consumption. During eclipse periods, the satellite uses a 78 AH Li-ion battery. SMOS has a launch mass of 658 kg: a 275 kg platform, 355 kg payload, and 28 kg of fuel.

The SMOS satellite will deploy a new type of scientific instrument in space: a microwave imaging radiometer that operates between 1,400 – 1,427 MHz (L-band). The instrument is called Microwave Imaging Radiometer using Aperture Synthesis, or MIRAS, for short. MIRAS consists of a central structure and three deployable arms, and uses 69 antenna-receivers (LICEFs) for measuring microwave radiation emitted from the surface of the Earth. The instrument is the result of almost ten years of research and development.

Credits: ESA-AOES Medialab

The data collected by MIRAS needs to go through a validation process. The radiation received by the instrument is a function that depends not only on soil moisture and ocean salinity, other effects need to be considered when instrument data is converted into units of salinity and moisture.

Factors that have to be considered are the distribution of vegetation, the litter layer, the soil type, the varying roughness of the surface, and the physical temperature of the surface of the land and sea.

In order to quantify the effects of factors mentioned above, dedicated campaign activities were conducted. Ground-based and airborne instruments similar to the one mounted on SMOS were used to collect data that was correlated with in-situ observations made by large ground teams. Long-term observations were carried out from an oilrig platform in the Mediterranean and at the Concordia Station in Antarctica.

The Committee on Earth Observation Satellites (CEOS) has defined a number of levels for the SMOS Mission Data Products. They range from Raw Data to Level-3 Data Products, which are Soil Moisture and Ocean Salinity global maps. Level-3 data will be available from the SMOS Level 3/4 Processing Center in Spain.

Eurockot will provide the launch services for the SMOS mission. A Rockot launcher, which is derived from a Russian Intercontinental Ballistic Missile (ICBM) SS-19, will lift off from the Plesetsk Cosmodrome, 800 km north of Moscow. The Rockot launcher will inject the satellite in a 758 km quasi-circular orbit.

The CNES Satellite Operations Ground Segment and ESA/CDTI (Centro para el Desarrollo Technologico Industrial) Data Processing Ground Segment will be responsible for the SMOS mission ground segment.

Initially scheduled for 2008, the launch of the Earth Explorer SMOS satellite will take place some time from July to October 2009.

You can find more details about SMOS on the dedicated page on ESA’s web site.

Credits: ESA

After a successful launch from the Plesetsk Cosmodrome in northern Russia by a Rockot launch vehicle, GOCE has to go through a number of preparation stages before becoming operational and starting to collect three-dimensional gravity data all over the globe.

On April 6, 2009, the GOCE’s propulsion system was switched on. The system was confirmed to be operating normally. Two days later, on April 8, 2009, the gradiometer was switched on as well. The instrument started to produce data instantly.

“With the ion engine and the gradiometer working, we have started to tune the satellite and its instruments,” GOCE System Manager Michael Fehringer said.

The payload, an Electrostatic Gravity Gradiometer, consists of six accelerometers mounted in pairs on three perpendicular axes on an ultra-stable carbon-carbon structure. Measurements of the tiny differences in the readings from the accelerometer pairs will render very accurate results for the geoid altitude and the detection of gravity-field anomalies.

Given the unique payload onboard the spacecraft, GOCE has to provide an undisturbed environment for the instruments. Two additional accelerometers mounted on the velocity axes will control the two low-power xenon ion engines in order to compensate for the atmospheric drag. The ion engines each can provide only 1 to 20 milli-Newtons of thrust, which does not sound like very much, but it is enough to overcome the drag experienced by the spacecraft in orbit.

GOCE has been losing altitude at a rate of 150m to 200m a day, until May 26, 2009, when the spacecraft entered the drag-free mode.

Rune Floberghagen, ESA’s GOCE Mission Manager, stated that, “Knowing that the drag-free control system works perfectly means we now have everything in place to carry out the complex process of calibrating the gradiometer instrument. Once calibration has been completed we will be able to see the true excellence of GOCE’s gravity-field measurements.”

The instruments have to undergo a further six weeks of commissioning and calibration. Mission operations are scheduled to start in summer 2009.

You can read more about the GOCE mission on the dedicated page on ESA’s web site.

Credits: ESA

ESA is about to launch a satellite capable of measuring very small variations in the Earth’s gravitational field. Even if it is a common-sense assumption that the force of gravity on the surface of the Earth has a constant value, there are subtle variations caused by the rotation of the Earth, the position of the mountains and ocean trenches, and by the variations of the Earth’s inner density. Determining the variations in the Earth’s gravitational field will improve our knowledge of ocean circulation, and will also help to make advances in geodesy and surveying.

The Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite will measure the small variations of the gravitational field. GOCE is the most advanced gravity space mission to date. Scientists will build a detailed map of Earth’s gravity using data collected by GOCE.

Credits: ESA

In order to make accurate measurements, the GOCE satellite will orbit in a low altitude orbit, around 250 km above the surface of the Earth.

An elongated shape has been chosen for the satellite design to minimize the atmospheric drag. GOCE is five meters long, one meter in diameter, and has a mass of roughly 1050 kg.

The heart of the GOCE satellite is a scientific instrument called gradiometer. The gradiometer consists of three pairs of accelerometers, and it measures acceleration variations over short distances between proof masses inside the satellite. One important thing to mention here is that the calibration of the gradiometer takes place after launch. The reason? The instrument cannot be calibrated on the ground, under the force of gravity.

Credits: ESA

You can find out more about the calibration of the GOCE instrument by reading an interesting article on ESA’s website.

Daniel Lamarre, a Canadian national working at ESA’s European Space Research and Technology Centre (ESTEC), is the inventor and the developer of the method used for the calibration of the instrument. He won an ESA award for developing the calibration method.

The GOCE satellite will be launched from the Plesetsk Cosmodrome in northern Russia. Eurockot Launch Services GmbH, a company that provides commercial launch services with the Rockot launch system, will be the launch provider for the GOCE mission. Eurockot was formed in 1993. EADS Astrium, located in Bremen, Germany, holds 51 percent of the company. The Khrunichev State Research and Production Space Center in Moscow, Russia, owns the remaining 49 percent.

Credits: ESA

The Rockot launcher is based on the SS-19 Intercontinental Ballistic Missiles. The upper stage of the launch system, Breeze KM, extends the performance capabilities of the Rockot lower stages. The system is capable of injecting a 1950 kg payload into Low Earth Orbit (LEO). The re-ignitable main engine of the Breeze KM allows various injection schemes for the payload. The length of the launch vehicle is 29 meters, with a launch mass of 107 tons. The external diameter of the three stages is 2.5 meters, while the payload fairing has an external diameter of 2.6 meters and a height of 6.7 meters.

The initial launch date was postponed due to an anomaly identified in the guidance and navigation subsystem of the Breeze KM upper stage. The new launch date has been scheduled for Monday, October 27th, 2008.