The NDVI3g time series is an improved 8-km normalized difference vegetation index (NDVI) data set produced from Advanced Very High Resolution Radiometer (AVHRR) instruments that extends from 1981 to the present. The AVHRR instruments have flown or are flying on fourteen polar-orbiting meteorological satellites operated by the National Oceanic and Atmospheric Administration (NOAA) and are curren...

A method has been developed to use a time series of relative position measurements to estimate the orbits of two satellites along with corrections to the gravity model of the celestial body about which they orbit. This system provides autonomy or near autonomy and could be used for gravity recovery at the Moon or a planet. This system eliminates the need for a third spacecraft that maintains a ...

[1] Using densities measured by accelerometers on the CHAMP and GRACE satellites, and taking advantage of the local time precession characteristics of these near-polar orbiting satellites, exosphere temperatures are derived as a function of local time, longitude and latitude. Significant longitude variability (e.g., ±25K maximum to minimum over the equator) in geomagnetically-quiet exosphere te...

1.1 GPS – benefits & constraints The Global Positioning System (GPS) is an all-weather, global, satellite-based, roundthe-clock system developed by the U.S. Department of Defense, which since the early 1980s has been available to the civilian community and has truly revolutionized navigation, surveying and geodesy. GPS is based on a constellation of up to 30 satellites orbiting the Earth, broad...

The space robot is the indispensable tool for future space activities such as building and operation of the international space station, inspection and repair of orbiting satellites, and conducting lunar/planetary explorations. The rendezvous docking technology to meet and to connect two spacecraft in-orbit is also an essential technology for the future space missions such as logistic support o...

New redshift surveys of galaxies in the field of compact groups have discovered a population of faint galaxies which act as satellites orbiting in the potential well of the bright group. Here we analyze the mass distribution of the groups by comparing the mass derived from the bright members and the mass obtained from the satellite galaxies. Our analysis indicates the presence of a dark halo ar...

In this paper are described the image processing algorithms developed by SENER, Ingeniería y Sistemas to cope with the problem of image-based, autonomous rendez-vous (RV) with an orbiting satellite. The methods developed have a direct application in the OLEV (Orbital Life Extension Extension Vehicle) mission. OLEV is a commercial mission under development by a consortium formed by Swedish Space...

Agile Earth observation satellites are satellites orbiting Earth with the purpose to gather information of the Earth’s surface by slewing the satellite toward regions of interest. Constraints arise not only from dynamical and kinematic aspects of the satellite and its sensors. Regions of interest change over time and bad weather can conceal important observation targets. This results in a const...