Colorado Space Grant Consortium

housed at the University of Colorado Boulder, working with students on campus as well as across the state on

The accuracy of atmospheric density measurements inferred from satellite drag is limited by errors in drag coefficient estimates. In this work, we use a unique opportunity in which the Drag and Atmospheric Neutral Density Explorer satellite and three Polar Orbiting Passive Atmospheric Calibration Spheres are deployed from a common launch vehicle. Each object flies through similar atmospheric conditions but has a different area-to-mass ratio. This allows aerodynamic analysis that is independent of atmospheric density via comparisons of measured and modeled ballistic coefficient ratios. A test particle method combined with a satellite energy accommodation model is used to model the aerodynamics of these objects. Fitted ballistic coefficients computed as a result of special-perturbations orbit analysis are then compared to the model results. The drag coefficient model and observations agree at the 1–2% level when coefficient ratios are compared. Comparisons of an additional shape with model predictions are made possible when one of the satellites shed its launch adapter. This work validates the aerodynamic model used here and can be applied in future research to improve models of atmospheric density and predictions of satellite drag. Beyond potential improvements to atmospheric models, the technique presented here is shown to identify objects based on their aerodynamic signature.

Future Earth and Space Science missions will address increasingly broad and complex scientific issues. To accomplish this task, we will need to acquire and coordinate data sets from a number of different instrumetns, to make coordinated observations of a given phenomenon, and to coordinate the operation of the many individual instruments making these observations. These instruments will need to be used together as a single ‘‘Virtual Mission.’’ This coordinated approach is complicated in that these scientific instruments will generally be on different platforms, in different orbits, from different control centers, at different institutions, and report to different user groups.Before this Virtual Mission approach can be implemented, techniques need to be developed to enable separate instruments to work together harmoniously, to execute observing sequences in a synchronized manner, and to be managed by the Virtual Mission authority during times of these coordinated activities. Enabling technologies include object‐oriented designed approaches, extended operations management concepts and distributed computing techniques.Once these technologies are developed and the Virtual Mission concept is available, we believe the concept will provide NASA’s Science Program with a new, ‘‘go‐as‐you‐pay,’’ flexible, and resilient way of accomplishing its science observing program. The concept will foster the use of smaller and lower cost satellites. It will enable the fleet of scientific satellites to evolve in directions that best meet prevailing science needs. It will empower scientists by enabling them to mix and match various combinations of in‐space, ground, and suborbital instruments − combinations which can be called up quickly in response to new events or discoveries. And, it will enable small groups such as universities, Space Grant colleges, and small businesses to participate significantly in the program by developing small components of this evolving scientific fleet.