Tag Archives: JT4G

Jun 6 2020

Longjiang-2 / LO-94: Journey to the Moon

Longjiang-2 / LO-94 in Lunar Orbit

Longjiang-2 / LO-94 in Lunar Orbit

A cartoon movie has been made that tells the story of the student-built spacecraft Longjiang-2 / Lunar-OSCAR-94 which went into lunar orbit and transmitted SSDV images back to radio amateurs on Earth.

SSDV image of Moon and Earth taken by LO-94 (Longjiang-2) - Credit Cees Bassa

SSDV image of Moon and Earth taken by LO-94 (Longjiang-2) – Credit Cees Bassa

Longjiang-2 / LO-94, developed by students and researchers at the Harbin Institute of Technology, is the world’s smallest spacecraft to enter lunar orbit independently. It was launched on May 20, 2018 and radio amateurs tracked its progress as it traveled towards the Moon and successfully entered lunar orbit.

The spacecraft transmitted signals back to Earth on 435.400 and 436.400 MHz. The amateur radio mode SSDV (Slow Scan Digital Video) was used to send back pictures of the Moon and WSJT JT4G was used for messages.

Two VHF/UHF SDR transceivers onboard were used to provide the beacon, telemetry, telecommand, digital image downlink and a GMSK-JT4 repeater, transmitting power was about 2 watts.

Watch Longjiang-2: Journey to the Moon

Harbin Institute Of Technology Amateur Radio Club BY2HIT
Weibo: http://www.weibo.com/by2hit
QRZ: http://www.qrz.com/db/BY2HIT

Oct 24 2018

LO-94 spacecraft signal decoded after bouncing off Moon

SSDV image of Moon and Earth taken by LO94 (DSLWP-B) - Credit Cees Bassa

SSDV image of Moon and Earth taken by LO-94 (DSLWP-B) – Credit Cees Bassa

Daniel Estévez EA4GPZ / M0HXM reports decoding a JT4G amateur radio signal from the LO-94 (DSLWP-B) spacecraft that was reflected off the Moon.

Daniel says “JT4G is a digital mode designed for Earth-Moon-Earth microwave communications, so it is tolerant to high Doppler spreads. However, the reflections of the [DSLWP-B] B0 transmitter at 435.4 MHz, which contained the JT4G transmissions, were very weak, so I had not attempted to decode the JT4G Moonbounce signal.”

However, by analysing a recording made on October 19, 2018 at 17:53:35 GMT he was able to decode one of the five JT4G transmissions in the recording.

Read his blog post at https://destevez.net/2018/10/dslwp-b-jt4g-decoded-via-moonbounce/

Also see Geometry for DSLWP-B Moonbounce
https://destevez.net/2018/10/geometry-for-dslwp-b-moonbounce/

The DSLWP amateur radio satellites built by students from the Harbin Institute of Technology was launched to Lunar orbit on May 20, 2018
https://amsat-uk.org/2018/05/19/dslwp-satellites-lunar-orbit/

May 19 2018

DSLWP amateur radio satellites launched to Lunar orbit

Hu Chaoran BG2CRY tests 435/2250 MHz dish feed for DSLWP ground station - Image credit Wei Mingchuan BG2BHC

Hu Chaoran BG2CRY tests 435/2250 MHz dish feed for DSLWP ground station – Image credit Wei Mingchuan BG2BHC

DSLWP is a lunar formation flying mission led by Harbin Institute of Technology for low frequency radio astronomy, amateur radio and education. It consists of a pair of 47 kg microsatellites launched from the Xichang Space Center into a lunar transfer orbit at 21:28 GMT on Sunday, May 20, 2018 and they will enter a 300 x 9000km lunar elliptical orbit. Onboard each satellite, there are two VHF/UHF SDR transceivers to provide beacon, telemetry, telecommand, digital image downlink and a GMSK-JT4 repeater. Onboard transmitting power is about 2 watts.

Update May 21, 2018: After deployment signals from the DSLWP satellites were received by Edson Pereira PY2SDR, Nicolás Castro CD3NDC, Robert Mattaliano N6RFM and many other radio amateurs around the world.

Chen Yue with 435/2250 MHz feed for the 12m dish at the DSLWP ground station - Image credit Wei Mingchuan BG2BHC

Chen Yue with 435/2250 MHz feed for the 12m dish at the DSLWP ground station – Image credit Wei Mingchuan BG2BHC

Wei Mingchuan BG2BHC reports the first launch window will open at about 21:28 GMT Sunday, May 20. The transmitters will be activated soon after separation. Satellite A will transmit 500 baud GMSK with 1/4 turbo code on 435.425 MHz and 250 baud GMSK with 1/2 turbo code and precoder on 436.425 MHz, and satellite B will transmit 500 baud GMSK with 1/4 turbo code on 435.400 MHz and 250 baud GMSK with 1/2 turbo code and precoder on 436.400 MHz, in every 5 minutes by default. Each transmission will last about 16 seconds. Radio amateurs in South America will have the earliest chance to receive the signals from the satellites, then North America, Oceania, Asia, Europe and Africa.

Harbin Institute of Technology Amateur Radio Club expects radio amateurs to join in this mission. We will prepare different QSL cards for different flight phase for amateurs successfully made QSO or received telemetry. Awards will also be given to the first 10 amateurs in each continent who successfully decoded the signals from the satellites, received the most number of packets, or received an image. Your participation will also help the team to get a better knowledge of the status of the satellites.

An open source decoding software based on GNU Radio to work with RTL-SDR and USRP is provided. Not difficult to change the grc files to support other SDR receivers. A small proxy software will send the decoded data to a server for real-time display.

IARU frequency coordination page:
http://www.amsatuk.me.uk/iaru/finished_detail.php?serialnum=530

Link budgets: http://lilacsat.hit.edu.cn/wp/?page_id=676

Decoder (GNU Radio OOT module): https://github.com/bg2bhc/gr-dslwp

Decoder (Linux Live CD): https://1drv.ms/u/s!Av6J6WjI3UbMhHm8gwMr4Z_keqWH

TLE: http://lilacsat.hit.edu.cn/tle/dslwp.txt

DSLWP-A Telemetry Display: http://lilacsat.hit.edu.cn/dashboard/pages_en/telemetry-a.html

DSLWP-B Telemetry Display: http://lilacsat.hit.edu.cn/dashboard/pages_en/telemetry-b.html

Wei Mingchuan BG2BHC Bug Fix 2018-05-20-1728-GMT: (Check BG2BHC Twitter feed for any further updates)

Sorry to find a bug in the DSLWP live cd! This bug will make the upload of data fail, so it is important to fix it. Please close the proxy, open a new terminal, and type in the following commands:

sudo python -m pip uninstall tornado

sudo python -m pip install tornado==4.5.3

The password is lilac
After running these commands, the bug should be fixed.

DSLWP Lunar Satellite

DSLWP Lunar Satellite