EUResearch have featured the work of EGSIEM and it's coordinator in one of their regular Success Story items, you can read the article here.
Euresearch is the Swiss network mandated by the State Secretariat for Education, Research and Innovation providing targeted information, hands-on advice and transnational partnering related to European research and innovation programmes.
Let’s suppose we wish to minimize a function of parameters, such as the sum of the squares of the residuals. We earlier supposed that the dependency of the residuals to the parameters was linear, and therefore the dependency of the function to the parameters is simply quadratic.
The GRACE monthly gravity fields are not perfect. Sensor and modeling noise are present in the solutions, the largest of which manifests itself as North-South striping. Filtering the solution eliminates a large part of the stripes and smoothing attenuates the noise, but of course not all the noise is removed. One way to evaluate the noise level in the monthly gravity field solutions is by analyzing the variations in equivalent water height (EWH) seen over regions with very little rainfall and hydrological mass redistribution.
Calculation of daily variations of the Earth's gravity field at GFZ
There has been a lot of improvement and development at GFZ during the past few weeks concerning the sensitivity of the applied Kalman process, enhancement of the data screening, reduction of outliers etc and a new daily time series of variations of the Earth's gravity field is well under its way to be delivered for evaluation purposes (e.g. to our colleagues from hydrology), soon.
The acceleration approach – an alternative way of processing GRACE data
What is the acceleration approach?
The acceleration approach is based on Newton’s equation of motion, i.e. the kinematic observations are linked to the dynamics = forces. Practically it means that we either need to observe accelerations directly, e.g. by accelerometers, or we need to derive them from other type of observations e.g. by numerical differentiation from positions. Since we are interested in the recovery of one particular force, namely the gravity field and its temporal variations, all other forces need to be subtracted by using e.g. models.
Since all Earth observing systems must refer to one and the same reference frame, the establishment of an improved reference frame is an important prerequisite for precise orbit and gravity field determination, and Earth studies in general. Based on improved models we have at AUIB started to process data from more than 250 globally distributed stations belonging to the network of the International GNSS Service (IGS). The time span of the processing is covering the period from 1994 to recent years. Additionally, to ensure high quality products for the purposes of EGSIEM, the orbital products are validated using Satellite Laser Ranging (SLR) observations.
EGSIEM aims at using gravity field analysis for forecasting and mapping of hydrological extremes like large-scale draughts and flood events. Observations of the redistribution of water and ice mass derived from the current GRACE mission, the future GRACE-FO mission and additional data are not part of the inventory of EO data products to date, although they constitute a new and unique remote sensing opportunity with innovative approaches to flood and drought monitoring and forecasting. Traditional earth observation resources for monitoring large scale disasters and disaster response based on weather satellites or optical and SAR satellites are provided by mechanisms and services such as the International Charter, the European Copernicus Emergency Management Service or Sentinel Asia, for example. This year the International Charter "Space and Major Disasters“ celebrates its 15th anniversary.
As you may have already discovered from the previous blog entries on the EGSIEM site, the Earth’s gravity field is a fascinating thing. Since gravitation itself is a pretty abstract concept, one might ask how do we actually visualize our gravity field solutions. Some representations like gravity maps (Figure 1)
"Attitude is a little thing that makes a big difference." Sir Winston Churchill
The precise attitude determination and control (ADC) is one of the key tasks for almost every satellite mission. Attitude determination is a process of estimating the attitude based on sensor measurement. Attitude control is then a process of maintaining or changing the attitude using either natural forces or actuators. The attitude is to be distinguished from the position. The position of a spacecraft informs us about where the satellite’s center of mass is located in space, whereas the attitude describes the motion about this center of mass.
Last week’s hot spell over large parts of Europe may have triggered memories of the heatwaves in the summers of 2003 and 2006. Over a number of days many European cities recorded peak temperatures in the year thus far, including Madrid (39.9 °C), Paris (39.7 °C), Berlin (37.9 °C) and London-Heathrow (36.7 °C). While definitions may vary somewhat regionally, a heatwave is generally described as a period of a number of consecutive days when the daily maximum temperature exceeds the average maximum temperature or a set maximum temperature by a set number of degrees. According to the World Meteorological Organization a heatwave occurs “when the daily maximum temperature of more than five consecutive days exceeds the average by 5 °C, the normal being 1961-1990.” If last week’s weather conditions signaled the start of a period of drought in Europe, however, is yet another story.
The EGSIEM Plotter development team is delighted to announce some brand new features which have been added to plot.egsiem.eu, these include:
- GRACE monthly gravity data has been incorporated from Universität Bern (UBERN), Centre national d’études Spatiales (CNES), Center for Space Research, The University of Texas at Austin (CSR), Deutsche GeoForschungsZentrum (GFZ), Jet Propulsion Laboratory (JPL) and Technische Universität Graz (TUG)
