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4M Lunar Flyby Spacecraft, Amateur Radio Payload Still in Earth Orbit; Future Mission Considered


The Amateur Radio payload on the Luxspace (LSE) Manfred Memorial Moon Mission (4M) lunar flyby experiment likely will continue to transmit for a few more days while it remains in Earth orbit. The Chinese Chang’e 5T-1 lunar mission payload that it initially accompanied into space on a Long March 3C rocket already has been recovered. The 4M was reported on November 6 to be some 248,000 miles from Earth with signals being “copied quite well” using a 2 ×8 element Yagi and a low-noise amplifier. The cells powering the spacecraft have been predicted to hold up for a few days. The 4M and Chang’e 5T-1 — part of the China Lunar Exploration Program — launched into space on October 23, with the 4M payload hitchhiking on the launch vehicle’s third stage. The Amateur Radio payload has been transmitting a WSJT JT65B beacon and telemetry on 145.980 MHz throughout 4M’s journey to the Moon and back, and it’s only by chance that the 4M managed to attain Earth orbit on the return leg, rather than burn up in the atmosphere — which had been its more likely fate.

LSE’s Ghislain Ruy, LX2RG, explained that the 4M project was “entirely funded by our company, with strictly no commercial purpose.” That, he said, required the project to be “cheap, fast, and efficient.” Several partner companies provided free or discount-price services.

“I had only 6 months to set it all up, starting from a blank page,” he said, pointing out that 7 months ago he “knew nothing” of JT65B. Ruy said LSE used the project as an opportunity to help train the company’s younger, less-experienced engineers. “Here at Luxspace are quite a lot of skilled, high-level engineers, and, to tell the truth, we do not object to having fun,” he said, adding that 4M has been “quite an education.”

“The next mission will integrate all what was discovered and learned,” Ruy told ARRL, adding that he’d like very much to include a second, similar Amateur Radio payload on the next mission, “if volume and antenna accommodations allow.” For now, he said, “4M has exceeded its planned lifetime,” although he declined to forecast how much longer it would remain in space.

The next LSE mission will not rely on Amateur Radio for telemetry but use the company’s own ITU-coordinated frequencies, Ruy said, while not ruling out a “small, amateur payload, similar to 4M, if available volume and power allow for that.” He’s hoping that the possible future payload would be smaller than 4M, but, if coupled to “a decent antenna” would be more efficient. The 4M uses a quarter-wave “tape measure” monopole antenna.

Attaching the 4M payload to the last stage of the Long March 3C rocket, Ruy said, “had a lot of drawbacks — some of them terrible,” but it kept down costs. Only the Chang’e 5T-1 was tracked, and not the last stage, so LSE engineers were only able to estimate the 4M’s lunar transfer orbit injection prior to launch. Other factors, including venting of the last stage’s fuel to avoid subsequent explosion and debris generation, can affect the trajectory. “Suffice it to say that there were some uncertainties,” Ruy told ARRL.

In the case of the lunar transfer orbit, though, such small changes early on “made all the difference” after the lunar flyby injection. The 4M appeared to have an injection that was closer to that of Chang’e 5T-1 than engineers’ estimates. In short, owing to these small differences, Chang’e 5T-1 was able to re-enter Earth’s atmosphere, while 4M did not.

“4M was made [as] a hands-on experiment, [to] get a practical grasp of the problem, albeit without much success, but [which] clearly taught us which way to follow from now on,” Ruy said.




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