Lunar Gateway

  • Image: NASA

    Hi All,

    The ham radio payload on the future Lunar Gateway will be interesting.

    At the recent AMSAT-NA symposium we heard:

    10 GHz downlink.

    100 Watts

    DVB-S2 DATV, etc.

    Existing QO-100 receivers should be able to receive the signals from the Lunar Gateway.

    Tests could be done now already with the DL0SHF moon beacon.

    Please ensure this important moon beacon is operational for 10 GHz receiver testing world wide.

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  • Image: NASA

    Here is a "back of the envelope" link budget calculation by Ron, W6RZ.

    For the downlink only.

    Here's a rough link budget. The Earth subtends an arc of about 2 degrees from the Moon, so a 1 foot dish on the gateway is about as large as it can get and still cover the entire Earth. So about 29 dBi of gain.

    100 watts = 50 dBm

    1 foot dish EIRP = 79 dBm

    Worst case path loss at 10.45 GHz = 225 dB

    power density on Earth = -146 dBm

    Noise floor at 29K and 10 MHz bandwidth = -114 dBm

    1 meter dish gain = 39 dBi

    Signal at DVB-S2 receiver = -107 dBm or 7 dB above noise.

    7 dB S/N could support 8PSK at 2/3 rate, which would provide 16.5 Mbps. Enough for several HDTV channels.

    Or a 0.5 meter dish could work at QPSK 1/2 rate, which would provide 8.2 Mbps.

  • Hmmm. Am I the only one who is a little sceptical about this project?
    I recall hearing the same optimistic plans about amateur radio onboard the ISS.

    The reality turned out to be some very expensive patch antennas on Columbus and the 2m / 70cm being used 99% of the time for NASA publicity via schools contacts, where the amateur radio contribution is sometimes invisible.

  • Hi David, I am sorry that you feel so pessimistic about the ARISS program. It actually has been a major succesful initiative to get kids involved in STEM and amateur radio. In addition, thousands of ham radio operators have over the years put ISS RX/TX ground stations together to facilitate a school contact with the crew on the ISS. Contrary to your assessment, the amateur radio contribution is highly visible and well recognized by local, regional and national press! in addition, new equipment is currently being prepared for the ISS and will get voice and digital communications upgrades installed. So, stay posted and maybe get involved with a local school and host a contact. I bet the kids could learn a lot from you sharing your experience and allowing them to have a once in a lifetime opportunity.

    73, Stefan VE4SW

  • At least we can try to push things into the right direction this time..

    AMSAT-DL (as part of the ARex Team) is also involved in the NASA Artemis Lunar Gateway activities. Some proposals have been submitted to ESA, also linked to AMSAT's expertise in general.

    Achim DH2VA is representing AMSAT-DL in the regular meetings and two years ago Achim already proposed link calculations and station setup with lessons learned from P4-A/QO-100 ground-station equipment. Which is the "easy sat" now..

    ISS and the Lunar Gateway will also be covered on Sunday on our

    AMSAT-DL Satellite Symposium 9./10. November in Bochum.

    Peter Gülzow | DB2OS | AMSAT-DL member since 1983 | JO42VG

  • TLDR: having the possibility to use a high gain antenna on the gateway compared to QO-100 global beam compensates for the 20dB more path loss. It will be +- identical in terms of ground equipment.. more details to follow in one of the next journals :)