Radio Science Experiment

The radio science experiment will use Doppler tracking to determine acceleration of the spacecraft by Eros' gravity on NASA's NEAR mission. The radio science experiment has no dedicated instruments, instead it uses instruments that will be used for other purposes as well. The mass of Eros can be determined from the orbital period and distance of the orbit obtained from the radio science experiment, images from MSI, and distance measurements from the Laser Rangefinder. Doppler tracking will provide information necessary to calculate the density of Eros.

Doppler tracking is based on the same principle as the Doppler effect. The Doppler effect is the apparent change in wavelengths from a source which could be visible light. If an object is moving away from the observer, the waves will appear stretched out to longer wavelengths. If an object is approaching the observer, the waves will appear closer together forming shorter wavelengths. Doppler tracking is used to determine the direction of movement of the object being measured, along with determining the object's acceleration.
Lesson Plan on the Doppler Effect

Radio Science Overview on NEAR Web Server

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