Gene L. Goltz

The Cassini gravitational wave experiment

Doppler tracking experiments using the earth and a distant spacecraft as separated test masses have been used for gravitational wave (GW) searches in the low-frequency band(~0.0001-0.1 Hz). The precision microwave tracking link continuously measures the relative dimensionless velocity, Δv/c, between the earth and the spacecraft. A GW incident of the systems produces a characteristic signature in the data, different from the signatures of the principal noises. For 40 days centered about its solar opposition in December 2001, the Cassini spacecraft was tracked in a search for low-frequncy GWs. Here we describe the GW experiment, including transfer functions of the signals and noises to the Doppler observable, and present noise statistics and compare them with the pre-experiment noise budget.

The Challenges and Opportunities for International Cooperative Radio Science; Experience with Mars Express and Venus Express Missions

Radio Science is an opportunistic discipline in the sense that the communication link between a spacecraft and its supporting ground station can be used to probe the intervening media remotely. Radio science has recently expanded to greater, cooperative use of international assets. Mars Express and Venus Express are two such cooperative missions managed by the European Space Agency with broad international science participation supported by NASAs Deep Space Network (DSN) and ESAs tracking network for deep space missions (ESTRAK). This paper provides an overview of the constraints, opportunities, and lessons learned from international cross support of radio science, and it explores techniques for potentially optimizing the resultant data sets.

First deep space operational experience with simultaneous X- and Ka-bands coherent tracking

This paper describes the new DSN science capability and highlights of the engineering work that lead to its development. It will also discuss experience with operations along with statistics and data quality.