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WG3K > ANS 12.02.24 16:12z 20 Lines 4203 Bytes #999 (0) @ AMSAT
BID : $ANS042.4
Read: GUEST
Subj: JS1YMG: Decoding the First Moon-Based Ham Radio Station's Te
Path: HB9ON<IW8PGT<IZ3LSV<DB0ERF<DB0RES<ON0AR<GB7CIP<KA1VSC<WG3K
Sent: 240212/1543Z 808@WG3K.#SMD.MD.USA.NOAM LinBPQ6.0.24
JQ1ZVI (JAXA Ham Radio Club, JHRC) recently obtained a radio station license from Japan for the lunar rover LEV-1, designated JS1YMG, marking a historic moment as the first amateur radio station on the moon. This milestone achievement follows Japan's SLIM lunar mission, which saw the deployment of two lunar excursion vehicles, LEV-1 and LEV-2.
LEV-1, designed for hopping mobility, features direct-to-Earth communication capabilities via UHF band antennas from the MINERVA and OMOTENASHI projects. Equipped with two wide-angle visible light cameras, LEV-1 conducts lunar exploration while carrying essential science payloads, including a thermometer, radiation monitor, and inclinometer, providing valuable insights into lunar conditions and terrain. It actively receives data from its companion rover LEV-2, and this information is transmitted to Earth using its 1 Watt UHF circular polarization antenna, employing Morse code on a IARU coordinated frequency of 437.410 MHz.
[cid:image004.jpg@01DA5B8E.5A386560]https://www.amsat.org/wordpress/wp-content/uploads/2024/02/JAXA_SLIM_LEV1_LEV2_Lunar_Rovers.jpg
https://www.amsat.org/wordpress/wp-content/uploads/2024/02/JAXA_SLIM_LEV1_LEV2_Lunar_Rovers.jpgJAXA's SLIM mission delivered probes, LEV-1 and LEV-2, to the lunar surface. [Credit: Japan Aerospace Exploration Agency]
Decoding efforts by Daniel Estévez, EA4GPZ, and others have shed light on the telemetry data transmitted by LEV-1. Utilizing captures from the 25-meter radio telescope at Dwingeloo in the Netherlands, Estévez identified the telemetry format as PCM/PSK/PM with a symbol rate of 64 baud and a 2048 kHz subcarrier. The residual carrier is modulated in amplitude with Morse code, introducing an unusual element to the signal. Despite challenges posed by amplitude shift keying in the signal, a phase-locked loop (PLL) has proven effective in tracking the phase of the residual carrier.
Estévez's decoding journey involved unraveling the CCSDS coding, a task that posed initial challenges. While the IARU coordination sheet hinted at bitrates and coding specifics, the signal's unique characteristics required a thorough investigation. The BCJR decoder, a tool used successfully in previous decoding efforts, validated the presence of convolutional coding. The output provided log-likelihood ratios, offering confidence in the correctness of the convolutional code. Further investigations led to the identification of the syncword 0xFAF320, a crucial element in understanding the structure of the transmitted frames.
[cid:image005.jpg@01DA5B8E.5A386560]https://www.amsat.org/wordpress/wp-content/uploads/2024/02/LEV-1_Demodulator_GUI_Daniel_Estevez.jpg
https://www.amsat.org/wordpress/wp-content/uploads/2024/02/LEV-1_Demodulator_GUI_Daniel_Estevez.jpgGNU Radio LEV-1 Demodulator GUI displaying Residual Carrier Amplitude from LEV-1 [Credit: Daniel Estevez, EA4GPZ]
One intriguing aspect of the decoded data is the Morse code modulating the residual carrier in amplitude. Despite initial confusion caused by an inverted amplitude representation, subsequent analysis revealed recognizable Morse code sequences. The meaning behind these Morse code transmissions remains a mystery, inviting collaboration from the broader radio amateur community and the LEV-1 team. As decoding efforts continue, the telemetry data's contents remain unknown, emphasizing the need for more documentation from the LEV-1 team. The spacecraft's utilization of the amateur satellite service and its completion of the IARU coordination process suggest that technical documentation may become publicly available in the future.
More details on the ongoing efforts to decode LEV-1's amateur radio transmissions can be found at Daniel Estévez's website at https://destevez.net/2024/01/trying-to-decode-lev-1/.
This achievement in establishing the first amateur radio station on the Moon opens up new possibilities for lunar communications and amateur radio enthusiasts worldwide. The collaborative efforts of radio amateurs contribute significantly pave the way for future advancements in space communication technologies.
[ANS thanks Daniel Estévez, EA4GPZ, and Hackaday for the above information]
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