An Application Of The Doppler Data For Interplanetary Mission
- Paper number
IAC-07-C1.5.09
- Author
Dr. Tsutomu Ichikawa, Japan Aerospace Exploration Agency (JAXA)/ISAS, Japan
- Year
2007
- Abstract
Recent improvements in computational capability interest in examining the possibility of using one-way Doppler data alone to navigate interplanetary spacecraft. The one-way data can be formulated as the standard differenced-count Doppler or as phase measurements, and the data can be received at a single station or differenced if obtained simultaneously at two stations. A covariance analysis, which analyzes the accuracy obtainable by combinations of one-way Doppler data, is performed and compared with similar results using standard two-way Doppler and range. The sample interplanetary trajectory used was that of the Planet-C mission to Venus. It is shown that differenced one-way data are capable of determining the angular position of the spacecraft to fairly high accuracy, but have relatively poor sensitivity to the range. When combined with single-station data, the position dispersions are roughly an order of magnitude larger in range and comparable in angular position as compared to dispersions obtained with standard two-way data types. It was also found that the phase formulation is less sensitive to data weight variations and data coverage than the differenced-count Doppler formulation. Outline: With increasing emphasis on controlling the costs of deep space missions, several options are being examined that decrease the costs of the spacecraft itself. One such option is to fly spacecraft in a noncoherent mode; that is, the spacecraft does not carry a transponder capable of coherently returning a carrier signal. Historically, one-way Doppler data have not been used as the sole data type due to the instability of spaceborne oscillators ( Ultra stable oscillator is carried in Planet-C spacecraft ) , the use of X-band frequencies, and the corresponding error sources that could not be adequately modeled. However, more sophisticated modeling ability, the possibility of using one-way Doppler is being reexamined. This article assesses the navigation performance of various one-way Doppler data types for use in interplanetary missions. As a representative interplanetary mission, the Planet-C spacecraft model and trajectory were used to perform the analysis. Comparisons are given between results employing Doppler data formulated as standard differenced-count Doppler (which yields a frequency measurement) as well as accumulated carrier phase (which yields a distance measurement, usually given in terms of cycles). Combinations of one-way data obtained simultaneously at two different stations and then differenced (to produce an angular type measurement) and single-station one-way data are shown to produce results that may satisfy future mission requirements.
- Abstract document