HAMTV from the ISS
The original HamTV unit was installed on the ISS in 2013 and commissioned in April 2014 and was used for a number of ARISS schools contacts in 2016 - 2018.
The unit failed in 2019 and was shipped back to Kaiser Italia for repair.
Following repairs carried out last year it now looks likely that the original HAMTV unit will be returned to the ISS with potential commissioning by a visiting astronaut during Spring 2024.
What is HamTV
HAMTV is the name of the Digital Amateur Television (DATV) transmitter on board the Columbus module of the International Space Station (ISS).
It transmits Digital video and audio in MPEG-2 format using the DVB-S protocol in the 13cms band .
HAMTV specifications
Ham Video downlink frequencies
- 2395 MHz (main operating frequency)
- 2369 MHz
- 2422 MHz
- 2437 MHz
DVB-S modulation
- Symbol rates: 1.3 Ms/s and 2.0 Ms/s
- FEC : ½
RF output
The HAMTV transmitter produces 10 watts RF, however this is then fed through a series of interconnecting cables and bandpass filter before passing through the ISS Columbus module external wall. Estimated power at the antenna is ~ 2 watts.
HAMTV antenna
The HamTV transmission runs relatively low power on 2395MHz to a simple patch antenna on the ISS.
This patch antenna is located on the earth side of the ISS but is surrounded by solar panels, thermal radiator panels, two or more visiting vehicles and robotic arms.
The ISS also “flies” slightly nose down to protect the cupola windows from space debris and so the RF performance, particularly when it is rising from the west, is slightly unpredictable.
The transmissions are right hand circular polarised (RHCP)
Video format
- NTSC
- SIF resolution: 352×240 or D1:720×480
What is HAMTV used for?
The primary use is during ARISS schools contacts, when the astronaut will use a camera to show himself and the inside of the ISS during the VHF radio contact.
It is hoped that test patterns, including JPEG images, will be transmitted when the cameras are not in use.
When will HAMTV be "on the air"?
It is unlikely that the HamTV transmitter will be on air 24/7.
During the first flight on the ISS between 2014 and 2018 it was used primarily for ARISS schools contacts but transmitter was left on at other times but no video was transmitted. This did allow groud stations to test their receive equipment and it is hoped a test signal generator will be included when it is re commissioned in 2024.
Once re-commissioned it will be tested before contacts and will be added to the Amsat status page https://www.amsat.org/status/
How to receive HAMTV?
There are a number of challenges to receive HAMTV from the ISS and a typical ground station is made up of the following elements
A typical groundstation system block diagram
Antenna
The HamTV transmission runs relatively low power on 2395MHz to a simple patch antenna on the ISS. This patch antenna is located on the earth side of the ISS but is surrounded by solar panels, thermal radiator panels, two or more visiting vehicles and robotic arms. The ISS also “flies” slightly nose down to protect the cupola windows from space debris and so the RF performance, particularly when it is rising from the west, is slightly unpredictable.
This means an antenna with reasonable gain is required to receive the signal and whilst it is possible to receive the signal on a simple antenna when the ISS is overhead, to enable more than 5 minutes of reception, a higher gain antenna such as a dish with an efficient feed system is required.
A 1 m or larger dish is optimum but smaller antennas such as flat plate or patch antennas will work and have the advantage of a wider beamwidth making it easier to track the ISS.