Wednesday, 3 August 2011

ARISSat-1/KEDR SSTV Signal



Okay bersedia semua, pada jam 1430UTC 3 Ogos, 2011. ARISSat-1 akan di active kan.

The ARISSat-1 FM downlink on 145.950 MHz includes live SSTV images as part of the cycling voice ID, select spoken telemetry values, and the international greeting messages. Here are some pointers to help you get your station ready to receive and display the SSTV pictures transmitted by ARISSat-1.



One fun feature is that there are four SSTV cameras mounted on the spacecraft. On photos of ARISSat-1 you may have noticed black brackets on the outside of the spacecraft. These hold the mirrors that reflect the light onto the lens of the cameras. The software-defined-transponder will use the image data from the cameras to generate the SSTV downlink.



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ARISSat's software will sequentially select a new or stored image from one the four cameras. There are two pre-recorded images as part of the sequence. The camera that took the the picture can be identified by the color of the call sign in the upper left of the SSTV image. The SSTV image will be sent down as FM audio SSTV in Robot 36 format on 145.950 MHz about every 140 seconds.

The RF downlink power on the 145.950 MHz FM downlink will be 250mW which is predicted to provide a link margin around 6 dB on an HT with a 'big whip' when the satellite is at 15 degrees elevation. This should be sufficient to receive SSTV pictures although you may need to orient the whip to line up the antenna polarization.

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ARISSat-1 is not stabilized so the antenna orientation is unpredictable and a certain amount of fading will happen. The receiving link margin may be improved with a handheld beam such as a commercially available "Arrow", "Elk" antenna., The WA5VJB "Cheap Yagi" antenna web pages document how you can build your own.

See the news bulletin regarding tips and pointers for the audio interface between your radio and your computer's sound card. When running your SSTV software just adjust the sound card audio gain slider and/or radio volume control so that the SSTV signal is within the center part of the bar. MMSSTV will give you an "overflow" indication if the volume is too high.



2 comments:

9W2KEY said...

1 antenna ARISSat-1 tercabut. Mission was aborted... Tak tau bila laa pulak benda ni akan dilancarkan

9W2KEY said...

ARISSat-1 was sucessfully deployed from the ISS at 1443 EDT today after a delay of a few hours from questions about the 70cm antenna.