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Radar image of the moon made with the Dwingeloo telescope

Submitter: Pieter-Tjerk de Boer
Description: CAMRAS uses the Dwingeloo telescope not only for astronomical observations, but also for contacting other radio amateurs via signals bounced off the moon (such transmissions are always coordinated with Astron to prevent interference).

An interesting combination of transmissions and astronomy is radar imaging of the moon. Of course, our transmit power of 65 watt (at 1296 MHz) is orders of magnitudes less than the peak pulse power employed for radar imaging elsewhere (e.g. at Arecibo). However, we can at least partially compensate for that by not transmitting pulses but a suitably modulated carrier.

The picture shows the result obtained using 15 minutes of radar reflections on August 7. The image is made using the "delay-doppler technique": signals reflecting off different parts of the moon's surface differ in delay (due to the moon's spherical shape) and Doppler shift (due to libration). The bright spot at the bottom represents the frontmost part of the moon, which is so bright because of specular reflection. The spherical shape of the moon can be inferred from the shape of the two "wings".

The resolution of the picture is currently limited by our transmitter, which is designed for voice transmission: it is not capable of high modulation frequencies (needed for improved delay resolution), nor of coherence in consecutive transmissions (needed for improved frequency resolution).
Copyright: Pieter-Tjerk de Boer / CAMRAS
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