CHAMP

CHAMP [Astrium]

CHAMP (Challenging Mini-Satellite Payload) is a German small satellite mission for geoscientific and atmospheric research and applications, managed by GFZ. With its highly precise, multifunctional and complementary payload elements (magnetometer, accelerometer, star sensor, GPS receiver, laser retro reflector, ion drift meter) and its orbit characteristics (near polar, low altitude, long duration) CHAMP will generate for the first time simultaneously highly precise gravity and magnetic field measurements over a 5 years period. This will allow to detect besides the spatial variations of both fields also their variability with time.

The three primary science objectives of the CHAMP mission are to provide

• highly precise global long-wavelength features of the static Earth gravity field and the temporal variation of this field.
• with unprecedented accuracy global estimates of the main and crustal magnetic field of the Earth and the space/time variablity of these field components
• with good global distribution a large number of GPS signal refraction data caused by the atmosphere and ionosphere, which can be converted into temperature, water vapor and electron content

Following instrumentation was used:

• Gravity: a new generation GPS flight receiver for continuous tracking of the low orbiter by the satellites of the GPS constellation for accurately and continuously monitoring of the orbit perturbations and a high-precision three-axes accelerometer for measuring the surfaces forces accelerations.
• Magnetics: a high performance Fluxgate magnetometer set measuring the three components of the ambient magnetic field in the instrument frame combined with a star camera determining the attitude of the assembly with respect to a stellar frame and a Overhauser scalar magnetometer serving as magnetic reference.
• Atmosphere/Ionosphere: the instrumentation used for the recovery of the magnetic and gravity fields constitutes at the same time a powerful assembly of sensors for observing many parameters relevant for the characterisation of the state and dynamics of the neutral atmosphere and ionosphere. GPS radio-occultation measurements can be used for the derivation of temperatur and water vapor profiles. Electric field measurements are performed with a digital ion drift meter. Electron density is determined by GPS radio sounding and the density of the neutral atmosphere can be estimated from measurements of the high resolution accelerometer.

For magnetic cleanliness reasons, the magnetometry assembly must be kept at some distance from the satellite. This is achieved by using a deployable boom mounted at the front end of the satellite. The length of the boom is approximately 4 m, thus guaranteeing that the magnetic strayfield at the location of the Overhauser magnetometer will be less than 0.5 nT

The boom consists of three segments: the outer part, carrying the Overhauser magnetometer, the middle segment with the optical bench on which two star sensor heads and two Fluxgate magnetometers are mounted, and the inner segment with the deployable part of the hinge.

CHAMP completed its mission and re-entered the Earth's atmosphere on 19 September 2010 after 10 years.