MSG: The next generation...
On august 29 2002 the first of a new generation weathersatellites was launced: Meteosat Second Generation.
Eventually this generation will replace the old Meteosat satellites, designed 25 years ago.
The data transmitted by MSG satellites differs a lot compared to the current first generation Meteosats:
|First gen. (MET7 and lower)||Second gen. (MET 8 and higher)
|Data format||APT (analog), HRI||LRIT, HRIT
|Data related to frame||Fixed: 4 or 8 frames/line||No relation: packets
|Bits coded||No||Yes; Viterbi
|Error correction||No||Yes; Reed Solomon
Because of the fixed data/frame relation, the straight-forward bit transmission and the absence of compression the HRI format is very simple to handle. It is even possible to plot the picture by means of a "picture drum", without the use of a computer.
This simplicity has also its draw-backs:
- Because of the fixed data/frame relation there is not much flexibility in transmitted picture sizes
- Because of the straight-forward bit transmission the sensitivity to noise is 'high'; the only way to increase the quality is by 'brute force': big antennas, powerfull transmitters and low-noise receivers.
- An errored bit is not corrected, not even recognized as such
- Because of the absence of compression the amount of data to transmit is high (i.e., the time to send one picture is long)
MSG transmits its data in a much more complex /sophisticated way, giving the following advantages:
Just like the old Meteosat sends its data in 2 flavours (APT, HRI)
MSG has also 2 flavours: LRIT and HRIT. These 2 digital formats are very similar.
Difference is that HRIT has 10 bits per pixel (LRIT: 8) and HRIT is lossless compressed (LRIT: lossy JPEG).
- Viterbi-encoding (K=7, n=2) gives 5 dB better sig/noise ratio, at a cost of 3dB more bandwidth
- By adding extra bits in each block of data error correction is possible
- JPEG compression can lower the amount of bits to transmit up to a factor 10
- The packet-like transmission makes it possible to efficiently transmit any size of picture, or other types of data, if needed.
Also, the modulation is different: BPSK for LRIT, QPSK for HRIT. Which means that the receivers for both formats are different.
Because of a burned-out transmitter in MSG1 all data is now distributed using the Hotbird satellite. Advantage for amateurs is that the equipment needed to receive MSG is very easy to get:
For the translation software I did make 'xrit2pic'. It is free available, see further on my website.
- A small dish, same type as used for satellite TV (80 cm, I use a 60cm offset disc aimed to Eurobird at 9 east)
- Skystar 2 TV tuner, pluggable into a PC (there is also a version to be connected via USB). Note: Other than skystar2 tuners are not guaranteed to work together with the Tellique software!
- A 'fast' PC (1GHz is more than enough) with 'lots' of disk space (with a 80G disk you can play a lot)
- Software to translate the data from the TV tuner into files on disk (Tellique software) and a key to decrypt the data, bot available at Eumetsat for in total 100 euro (amateur use only)
- Software to translate the files into viewable pictures
- ==> File
- Postprocessing: xrit2pic, weview etc.
Data is filtered by means of PID's One pid Must always be present:
The other PID's are optional:
- 100 (decimal): the message channel.
Tellicast: Who is afraid of red, yellow and purple?
Note: following info may not be complete, or even 100% correct.
A running tellicast will show a coloured T in your Icon bar.
It can show 3 different colours:
Note IP connection: This depends on what type of receiver you use.
- Yellow: Tellicast is trying to establish a connecion.
It stays yellow if no connection can be made, e.g. because:
- firewall blocks connection
- nothing received
- wrong satellite received
- PID 100 not enabled
- There is no ethernet route between receiver and Tellicast. See below
- Purple: OK, PID 100 Eumetcast data received.
- interface_address wrong (recv.ini; 0.0.0.0 is "always OK")
- Connection lost, i.e., there was a connection (purple T) but connection was lost
because of one of the reasons mentioned near Yellow T.
Note that if nothing changes the T stays red, but if you restart Tellicast the T becomes yellow! (Except if interface_address is wrong.)
So the only difference between yellow and red is the past.
Note: Following items do NOT influence your T-colour:
- missing/malfunction EKU
- wrong user address
- wrong password
- Ethernet receiver, like SR1 Ayecka: 2 possibilities:
- Use recv-channels.ini to choose which channels to receive: set interface_address=0.0.0.0 (in recv.ini)
- Choose by routing (e.g. using ecast_cfg on Linux): set interface_address to the destination address
of your choice and route all channels you want to receive to that address. Define in recv-channels.ini to receive 'everything'.
- USB receiver: this will use a dummy ethernet address which you can choose; it must be identical to what is in recv.ini. Common used:
Make sure that the EKU you use belongs to the user_name and user_key in your recv.ini.
If you don't have a key the define:
You will then only receive the 'free' data.
Deactivate start tellicast at boot (Windows).
Navigate using e.g. 'This computer' to:
At this place you should see an icon 'pink T', called 'BisinessTV-IP
- local station C:
- Documents and Settings
- Menu Start
Now Tellicast wil not start anymore a boot-time.
By moving the link back to the original place you can restore the auto-start-at-boot.
- Create a new directory, e.g. 'off'
- Move the link to this directory