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4M Moon Orbiter Signals “Quite Weak,” Onboard Messages to Loop


It’s getting to be more challenging to receive the JT65B transmissions from the recently launched 4M (Manfred Memorial Moon Mission) lunar payload. The 13-character onboard messages posted from around the world prior to launch were expected to be transmitted this week and will be repeated. On October 25 Ghislain Ruy, LX2RG, of LUXspace said signals from the 4M payload were quite weak.

“This is not due to a loss of power, as telemetry shows normal parameters, but to the attitude of the last stage that places a deep [null] of the radiation pattern in the direction of the Earth.” He expressed the hope that Earth’s movement with respect to the inertial attitude of the spacecraft’s last stage would yield better results in the days ahead.

“The 4M is becoming a real challenge now, and receiving the signals during flyby will be quite an achievement,” he said. He said those attempting to hear the 2 meter (145.980 ±Doppler shift) downlink signal will need high-gain antennas. He predicted that signals will be 4 dB weaker when 4M is in the vicinity of the moon.

Radio amateurs have been encouraged to receive and report the spacecraft’s signals. There is a tracking calculator. A 4M payload blog also is available.

More than 2 dozen Earth stations have been capturing the 4M datastream on a near-continuous basis. Another 100 have registered to file reports with the 4M data warehouse.

A Chinese Long March 3C/G2 rocket carried the Manfred Memorial Moon Mission (4M) lunar flyby experiment into space at 1759 UTC on October 23, on its way to a lunar transfer orbit and a return to Earth in about 9 days. Radio amateurs in Oceania and Europe were among the first to report hearing the JT65B signal from the onboard Amateur Radio payload. Lunar flyby is to occur, nominally, on October 28, and the Amateur Radio package will transmit continuously throughout the voyage.

During the lunar flyby, the spacecraft will be about nearly 248,000 miles from Earth and between 7440 and 14,480 miles from the Moon. The 4M Amateur Radio payload is transmitting a WSJT JT65B beacon and telemetry on 145.980 MHz.

The October 23 launch represents the third phase of China’s lunar exploration program. The Chang’e-5-T1 mission is aimed at validating technologies for a future lunar sample return probe. If successful, the mission will mark the first successful re-entry of a Chinese space vehicle into Earth’s atmosphere.

The mission honors the late Professor Manfred Fuchs, founder of LUXspace’s parent, the OHB group, who died earlier this year. The 4M-LXS ham radio package carries up to 2500, 13-character digital messages into space for retransmission. The International Amateur Radio Union (IARU) is a partner in the experiment. — Thanks to AMSAT-UK via AMSAT News Service




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