Finished Research Projects

Multisensor Climatology onboard GRACEThe thermosphere lies between the exosphere and the mesosphere. The temperature in this layer can reach up to 4,500 degrees Fahrenheit. The thickness of this layer is about 513 km [NASA, 2018]. The thermosphere is the top level of the Earth atmosphere, located from 100 to 1000 km altitude. At 100 km already, the air density is twelve orders of magnitude lower than at the Earth’s surface. However, the remaining air is enough to exert a significant force on satellites orbiting the Earth at low heights. This perturbation is mainly due to high orbital velocity of 7.5 km/s, and the proportional relation between the air drag and the square of the speed. Since the spaceborne accelerometer could measure the total nonconservative accelerations acting on the satellites directly, the air drag component could be isolated with the help of solar and earth albedo radiation pressure models, then the atmospheric density can be estimated, which provides necessary data for making evaluation and improvement of the existing atmospheric models.Leaders: Prof. Dr.Ing. Jakob Flury, Dr.Ing. Akbar ShabanlouiYear: 2018Lifespan: WiSe 2018/2019

Disentangling gravitational signals and errors in global gravity field parameter estimation from satellite observations (SFB 1128, C01)Rangerate residuals from the estimation of global gravity field parameters from GRACE satellitetosatellite tracking reveal a range of systematic effects that limit the accuracy of the estimated parameters. The project investigated the characteristics of time series of rangerate residuals. It addressed how drops in the Kband ranging signaltonoise ratio at specific intersatellite Doppler frequencies propagate to anomalies in rangerate residuals, as well as anomalies during penumbra transitions. A part of the project at TU Graz, in the group of Prof. MayerGürr, studied options to use wavelet parameters in the SST gravity field parameter estimation.Leaders: Prof. Jakob FluryTeam:Year: 2014Sponsors: DFGLifespan: 20142018

Highly physical penumbra solar radiation pressure modeling with atmospheric effectsDuring penumbra transitions of an Earth orbiter, the solar radiation hitting the satellite is strongly influenced by refraction and absorption of light rays grazing the Earth’s atmosphere. The project implemented solar radiation pressure modeling including these effects. Model results were tested by comparing with measurements of the accelerometers of the GRACE low Earth orbiters.Leaders: Prof. Jakob Flury, Tamara BandikovaTeam:Year: 2010Sponsors: RISE/QUESTLifespan: 2010

InOrbit System Analysis of the Gravity Recovery and Climate Experiment (GRACE) MissionPrecise determination and control of satellite attitude plays a key role for satellite geodesy in general, and for SatellitetoSatellite Tracking in particular. The project provided the first indepth characterization of GRACE pointing biases and pointing variations. Investigations addressed star camera interboresight angle variations, the weighted camera sensor head combination, as well as error propagation to intersatellite ranging and accelerometer observations. Results led to significant improvements in the operational GRACE data processing.Leaders: Prof. Jakob FluryTeam:Year: 2009Sponsors: Exzellenzcluster QUESTLifespan: 20092015© IfE / Bandikova