This paper investigates to what extent the relative orbital elements of two satellites flying in formation can be estimated making use of inter-satellite range measurements only. Since the determination of relative orbital elements does not require the orientation of the relative orbit with respect to absolute inertial space to be resolved, as would be the case for absolute orbital elements, the question arises whether relative range measurements alone can be sufficient to solve the problem of interest. Providing an answer to this question is both of academic and practical interest, especially for formation flying missions utilizing very small satellites that are limited in their capabilities. To this end, a linearized relative dynamics model is implemented using an iterative batch least-squares algorithm to estimate rectilinear relative positions and velocities, which are subsequently converted to relative orbital elements for a number of test cases. Furthermore, the observability of the system is analyzed to investigate which relative orbital elements are most observable. Nomenclature Roman Symbols

The paper treats the mission design for the Dutch-Chinese FAST (Formation for Atmospheric Science and Technology demonstration) mission. The space segment of the 2.5 year mission consists out of two formation flying micro-satellites. During the mission, new technologies will be demonstrated and, using spectropolarimeter and altimeter payloads on both spacecraft, observations will be performed characterizing atmospheric aerosols and seasonal variations of height profiles in the cryosphere. The mission is divided into four phases, each with a different orbital geometry. The rationale for and the orbital geometry during these phases as well as the transitions between the phases are treated in detail. A major complication to the mission design is the amount of data that can be sent to the ground. Since only two moderately capable ground stations, one in Delft and one in Beijing, are baselined, as much data processing as possible has to be performed onboard to allow high duty factors for the science payloads. When this is not possible, alternative payload operation modes have to be sought with which maximum scientific data return can be obtained through as little payload operation as possible. Both options are dealt with in the paper.

No abstract

Large current uncertainties in the characteristics of aerosols in the Earth's atmosphere preclude meaningful climate model evaluation. The FAST mission will contribute to the characterization of aerosols and their relation to climate change through a synoptic evaluation of local, regional and global aerosol data and altitude profiles of the cryosphere. The Dutch-Chinese mission will implement this objective through a unique combination of payloads onboard of two cooperating micro-satellites flying in formation in a Low-Earth Orbit. The FAST payload suite is unique in that it allows an unprecedented characterization of aerosols through a spectro-polarimeter instrument, which, when combined with radar and laser altimeter data, contributes to the characterization of the indirect climate forcing due to aerosols. Finally, flying instruments on two satellites in formation and, in a later mission phase, in a train configuration, allows an exceptional flexibility to study the temporal and spatial distribution and evolution of aerosols in the Earth's atmosphere.

No abstract