[TCRA] Slow scan TV images from the ISS this coming weekend

Rodney Anders wb9wkt at gmail.com
Sun Dec 20 09:22:28 CST 2015


Hello:

     Just want to let people know that the ISS (international space
station) may be sending slow scan images down to earth on Dec 26 and Dec
27.  You can record these passes then play them back by your computer
microphone and see what pictures were being sent down.

 All you need to do is monitor 145.800 and record the noise.  Then take it
inside and play it back by your computer program or app.

 Looking at the PASSES it will be during the day---which is way cool.  (see
the pass schedule below)

   The web will have a ton of information on all of this but here is a
quick list:

Program to decode:  I downloaded "MMSSTV" works slick.
Mode they use:          PD120
Freq to monitor:         145.800

I have also included the times of the passes this weekend along with a
brief write up of what might happen.  Sounds like its not 100% sure to
happen.
Its pretty cool to think we can capture images from the ISS which is moving
17,000 mph.

Give it a try--if you have any questions email me back.

Rodney Anders
wb9wkt

What to expect during a pass

SSTV mode PD120 will be used instead of PD180 which was used during
previous SSTV events this year. With PD180 it takes about 3 minutes to send
an image. With PD120 it takes about 2 minutes to send an image. Since
images transmitted with PD120 take less time to send than with PD180, more
images can be received during a single ISS pass.

An ISS pass that goes right overhead (90 degrees elevation), lasts about 10
minutes. ISS SSTV transmit time and off time are usually setup to provide
the radio with a 50% duty cycle (only transmit half the time so the radio
doesn’t overheat). With image transmission taking two minutes, off time
will probably be two minutes as well.

Compared to previous SSTV events using PD180, this means it should be
relatively easy to receive at least two complete images in one pass, with
the possibility to receive up to three images if timing, conditions, and
setup are ideal.

When the ISS comes into view/has line of sight with you, this is known as
Acquisition of Signal, or AOS. The ideal situation for a high elevation 10
minute pass would be if the first image started transmitting exactly at
your AOS, and you had a directional antenna so you could receive the signal
even while the ISS was very low in the beginning and end of the pass.

In this case you would be able to receive three images like this:

minute, image TX/off
0-2, complete image 1
2-4, off
4-6, complete image 2
6-8, off
8-9, complete image 3

The more common situation will be that the first image transmission will
start either before or after AOS. In this case you will only have the
opportunity to receive two complete images, but this is still twice the
amount of images that were possible with PD180. The downside is the image
quality is not as high as with PD180.





25 dec -        16:36:16    10°    WNW        16:39:29    52°    SW
16:42:42    10°    SE    daylight
26 Dec    -    09:17:38    10°    S            09:19:42    16°    SE
09:21:51    10°    E    daylight
26 Dec    -    10:52:32    10°    WSW    10:55:47    77°    NNW
10:59:04    10°    ENE    daylight
26 Dec    -    12:29:43    10°    WNW    12:32:35    27°    N
12:35:26    10°    NE    daylight
26 Dec    -    14:06:44    10°    NW        14:09:38    28°    N
14:12:33    10°    ENE    daylight
26 Dec    -    15:43:04    10°    WNW    15:46:22    89°    NNE
15:49:40    10°    ESE    daylight
26 Dec    -    17:20:35    10°    W            17:22:24    14°    SW
17:24:08    10°    SSW    visible
27 Dec    -    09:59:25    10°    SW         10:02:38    61°    SE
10:05:52    10°    ENE    daylight
27 Dec    -    11:36:13    10°    W            11:39:13    32°    NNW
11:42:14    10°    NE    daylight
27 Dec    -    13:13:28    10°    NW         13:16:15    25°    N
13:19:03    10°    ENE    daylight
27 Dec    -    14:49:54    10°    NW         14:53:09    54°    NNE
14:56:23    10°    ESE    daylight
27 Dec    -    16:26:38    10°    W            16:29:24    25°    SW
16:32:08    10°    SSE    daylight

How to read this.

December 26 @10:52:32 the ISS will be on the WSW horizon.  At 10:55:47 it
will be 77 degrees in the NNW  (0 degress is the horizon and 90 degress is
straight over head).  Then at 10:59:04 we will lose the signal in the ENE.

You can use a hand-held----point your radio WSW then when you hear it you
can track it.  When the signal starts to get fuzzy you need to point your
radio to the path.  it goes WSW-------NNW--------ENE  in about 8 minutes of
time.


Let me know if you have questions.

Rod



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