A contact between a radio amateur in Germany and China took place on July 1 via the moon-orbiting LO-4 satellite, DSLWP-B, launched in May 2018. The two-way exchange between Reinhard Kuehn, DK5LA, in Soerup, Germany, and Harbin Institute of Technology club station BY2HIT (operated by Wei Mingchuan, BG2BHC), in Harbin, China, occurred between 0551 and 0728 UTC, according to reports. The GMSK-to-JT4G repeater onboard DSLWP-B was used to make the contact, the first ever made via a lunar-orbiting repeater.
“Using the GMSK-to-JT4G repeater is not easy, in terms of the signal power needed for the uplink,” commented radio amateur and engineer Daniel Estévez, EA4GPZ, whose blog includes images of the lunar surface downloaded via DSLWP-B. “There were plans to make a QSO between BY2HIT and Reinhard since many months ago, but previous attempts didn’t work out. My congratulations to the people at both sides of the QSO, who have achieved it a month before DSLWP-B crashes against the lunar surface.”
As Estévez explained it, the GMSK-to-JT4G repeater works by sending commands to the satellite that embed a 13-character message, using the same frequency and a similar protocol to the one that commands the camera and other satellite functions. He said sending a message in this fashion takes a little longer than 1 minute.
An open telecommand protocol allows radio amateurs to take and download images, and DSLWP-B transmitted images of the moon and Earth during this week’s solar eclipse. DSLWP-B was launched as a secondary payload with the Quequiao relay satellite as part of the Chang’e 4 mission to the far side of the moon. Last September, some earthbound radio amateurs and sky watchers received images from the tiny satellite as it orbited the moon.
DSLWP stands for “Discovering the Sky at Longest Wavelengths Pathfinder,” and was designed to test low-frequency radio astronomy and space-based interferometry. The repeater uplink is on 2 meters and the downlink is on 70 centimeters.
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