Bruce Haines (JPL/Caltech, USA); Steve Nerem (University of Colorado, Boulder, USA); Richard Biancale (CNES, France)

The Geodetic Reference Antenna in Space (GRASP) mission concept will be proposed once more to NASA in response to the expected Earth Venture Mission (EV-M) call in 2015. GRASP was proposed for the 2011 EV-M call, and was ranked second among all submissions, primarily on the strength of its terrestrial reference frame science and the broad support it generated from the geodetic community. For the upcoming proposal opportunity we plan to potentially augment the original mission configuration, namely a collocation of GNSS, SLR, VLBI, and DORIS sensors on a supremely calibrated and modeled spacecraft, with payloads that enhance the geodetic science output. Among the technologies being entertained are: A GRACE-Class accelerometer and an Ultra Stable Oscillator. In addition, complimentary payloads that enhance the overall science productivity at little cost, such as GNSS radio occultations, are also considered for optimizing the cost to benefit ratio, and promoting cost sharing.

The potential cost increase due to the enhanced technical scope of the mission could be mitigated through cost sharing between collaborating organizations. A NASA-CNES partnership is emerging as a foundation for these collaborations, while additional collaborations are being actively pursued.

We will describe the recent simulations activities in support of the GRASP mission concept and discuss the various enhancements to the baseline mission from the addition of the above-mentioned payloads.