Iridium flares
TheSkyX
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Sample AVI Paramount Tracking bird*
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When the
geometry is just right (Sun - Satellite - Earth position) the sunlight hits one of
the Low Earth Orbiting Iridium (484 miles above the Earth) satellite's 3 main mission antennae and the reflection creates
a small cone of light that covers a small path over the Earth. When the cone
falls over your
location you can see the bright reflection of sunlight off the mirror
like surface. These flares only last for a matter of seconds! The flare is not caused by the solar panels but rather the
main mission antennae (3) which have a special Teflon coating used to
protect the antennae. The name Iridium comes from the periodic table
of elements where entry number 77 is Iridium. Originally there were 77 primary satellites in
the array allowing for all sky cell phone coverage. The array was placed
in orbit by
Motorola.
The
sunlight is coming in from the left side of the image below. The light
hits one of the 3 mission antennae and is reflected back to Earth. Cone NOT TO SCALE!!!
Crude image but effective!
Seeker graphics Illustration
with help from Adobe Photoshop
For those with
TheSkyX
PC/Mac now shipping and soon Linux you can make Iridium Flare
predictions quite easily. Download the TLE's for the Iridium satellites in
TheSkyX then use the flare prediction routines. See below. TheSkyX makes
it quite trivial to find out where and precisely when the flares occur. My
tests have shown the prediction times are good to 1 second in time or
better! This makes
it easy to share flares with friends and family. Note
TheSkyX
uses the Celestrak web site
for the source of the necessary Two Line
Elements (TLE's) used for calculating accurate satellite positions and
flare times.
HINT: If you go
directly to the Iridium Flares tab and don't have the necessary TLE's
needed to plot the satellites TheSkyX will attempt to automatically
download them from the Internet for you. This requires an internet
connection!
If an Internet connection is
not present you will have to download the TLE's to a file then use the
option to Import them from a file instead.
Press Find Flares
The TLE's are downloaded automatically via
the Internet!
WARNING!
You must have an internet connection established
first! If there is no connection you will have to ABORT the download
process!
NOTE!
Always double check the "Average age" of the TLE's reported on the
satellites dialog! If the date and time in TheSky are wrong the satellites
will be date rejected and will not plot!
TheSkyX Satellites
dialog TLE's have been downloaded
Import from the Web then double check
Average Age!
Once you have current
TLE's loaded you are ready to make predictions! These predictions are based on
the location you have set in TheSkyX! Make sure it is reasonably accurate.
The flare cone projected on planet Earth is reasonably small so make sure
the location is set the best you can! Use the web as a source of a GPS
receiver to set extremely accurate location. Also, enter your elevation if
possible. The predicted magnitude will change with elevation!
Find "Iridium Satellites" in
the list!
Then press Download
Note: You can also
choose to download more than one group in TheSkyX! Like the HST, ISS, Iridium's, Geo's
etc. Just check all you want keeping in mind the more the slower the
updates will be in TheSkyX!
Checking more than 1 group
Multiple groups selected
ALWAYS
double check your site information!
Input | Location and inspect after setting!
The more accurate the better!
Use the web or better yet a GPS
WARNING!
When using the automatic IP to
Lat/Long feature in TheSkyX via the Web to set your location
this does not guarantee you have an
extremely accurate location chosen automatically! Again for Flare Predictions you want
the best earth based location you can get for the best accuracy including
proper elevation, time zone, and Daylight saving option (DSO).
The Time Zone and Elevation
are also not properly set by the use of IP to Lat/Long or
even the Zip Code feature. Generally the Daylight Saving Option will be
correct when the correct city has been found, i.e. U.S. and Canada. Here the elevation has been
changed to 5,280 feet (1609 meters) for Golden Colorado. The elevation
will affect the magnitude estimate! Also note the default Time Zone for
Golden has been changed from -6 to -7 accordingly since a value of -6 was
set automatically. From then on TheSkyX
will take care of the daylight changes automatically. Again, you can spot
check your time zone and elevation via GPS or using the web to search by
your location.
After downloading a valid set
of TLE's for the Iridium array of satellites and
after double checking the site
information TheSkyX will make very accurate predictions for flares based on
the observer's location. Use Tools | Satellites then the Iridium Flares
tab on the satellites dialog to make predictions. You have control over
the prediction. You can search for Night flares, Daytime flares, Dawn/Dusk
flares or ALL flares.
HINT: Start by
searching for Nighttime flares these are the easiest to find!
Specify how many days to search for (no more then 30) and at what starting altitude.
If you have obstructions near by increase the altitude to something like
20 degrees or even higher (looking way up!). Usually searching for a week
at a time is best since the flares are not all that frequent. And if you
only want real bright ones limit the magnitude to a negative number like
-3 to -8. These are VERY bright but far less frequent but they are
much more impressive, last longer, and are easier to spot! The smaller the
magnitude the brighter the flare! -8 for a
magnitude is brighter then Venus which next to the Sun and Moon is the
brightest object celestial object in the sky. There is nothing like a mag
-8 flare!
Search criteria
Nighttime flares for a week
Limit search - start easy!
After pressing "Find Flares" flares
those that match the search criteria are shown. See
example below. If none are listed change the search parameters, i.e.
increase number of days.
Table of flares that
have been found based on the search criteria
Local Time UTC Magnitude Altitude Azimuth Angle Satellite Mirror Number Julian Date
3/21/2008 07:19:40 DST 2008-03-21T12:19:40Z -0.5 38 12 1.7 IRIDIUM 31 [+] 2 2,454,547.01366
3/21/2008 20:56:57 DST 2008-03-22T01:56:57Z -1.6 59 150 1.0 IRIDIUM 34 [+] 2 2,454,547.58122
3/22/2008 07:13:43 DST 2008-03-22T12:13:43Z -0.6 36 12 1.7 IRIDIUM 33 [+] 2 2,454,548.00953
3/23/2008 07:07:46 DST 2008-03-23T12:07:46Z -1.4 34 13 1.1 IRIDIUM 59 [+] 2 2,454,549.00539
3/24/2008 07:01:49 DST 2008-03-24T12:01:49Z -0.7 32 13 1.6 IRIDIUM 28 [+] 2 2,454,550.00126
3/25/2008 06:55:54 DST 2008-03-25T11:55:54Z -0.1 31 12 2.1 IRIDIUM 30 [+] 2 2,454,550.99715
3/25/2008 06:52:25 DST 2008-03-25T11:52:25Z -0.2 29 15 2.1 IRIDIUM 95 [S] 2 2,454,550.99473
You can sort the data by any
field you choose, date/time or magnitude. Click on a flare then you can
"WATCH" the flare simulation in real time using TheSkyX.
Choose a flare then
press "Watch Flare"
Or Create a Quick Time Movie!
And watch the show!
TheSkyX can even create Quick
Time movies of the flare! Click here
for samples rendered by TheSky!
Wow, how cool is that?
click on to enlarge!
Laser pointer shows position prior to flare
Example Quick Time movies Click here!
The laser pointer clearly
shows the satellite's position just before the flare. This makes it very easy to
find them. You need only be concerned with what direction to look and near which
constellation the flare occurs.
Another feature found in
TheSkyX is the ability to plot satellites in 3D space and even find best
passes for your location. Works great for the ISS or HST!
Iridium satellites
plotted in 3D space - TheSkyX
Two orbits are displayed
Satellite positions in space
change constantly. Therefore a current set of TLE's should be downloaded
very near if not on the date of the flare predictions for the best
possible accuracy. After 30 to 45 days the TLE's are obsolete and should
not be used. TheSky will date reject them.
Track on Satellite using
TheSky6
by matching the satellites changing rates!
WARNING!
The accuracy of the TLE's is
only good to several arcminutes. Meaning the satellites can be difficult
to place in fields of view smaller then about 15 arcminutes in size! This
is a limitation of the input source not TheSky's ability to calculate the
satellite's position.
Here the
Paramount ME
and C-14 were tracking on the satellite. Look closely and you
will see the trailing stars on the left. A 67 second CCD image using the
SBIG ST-9 was then taken near the flare predicted time. And yep it
was there. NOTE this is a VERY small field less than 10 arcminutes square!
The telescope pointing was off a bit
because there was no TPoint model and this is a VERY small field of view
and as stated the TLE's are generally only good to about 10 arcminutes. More to
come...
First Attempt so Flare with
me!
Tracking ON the satellite
First obtain the necessary
two line elements
(TLE'S) from the web. The most convenient way to do this is use
TheSky6's link to the Celestrak page. Also make sure the
date/time in question have been properly set in
TheSky!
Import From Web
Also apply "Plot Paths"
Choose Iridium Satellites
From the list
If your satellite download
requires a username/password download update to the latest version of
TheSky6
Hotfix for TheSky
which no longer requires this!
When you have the TLE's
download and the proper date and time set in TheSky6 you will see exactly where the
flare occurs. The following shows the satellite path BEFORE
and AFTER the flare. This makes finding the object much
easier. The label Iridium 60 falls exactly at the position of the
flare, note exact time of flare shown.
Now TheSky shows the spot
where the flare
occurs
Here is where
and when the flare occurs
After you have the necessary
Altitude and Azimuth coordinates and the date and time for when and where
the flare will occur for your location use the TheSky6's menu item Data | Add User Data to add a
new "Horizon coordinate" data entry. See below. Choose a Data Class of type "Labels" and
an Object Type of "Reference Point" as shown below. The label you
enter will be the Date and Time of the flare and this will be plotted on
the main sky display at the precise position where the flash occurs.
Label when and where the flare will occur
Enter a Horizon based coordinate
and label the date
and time
Use the "CENTER" button above to have TheSky
display centered on the field where the flare will occur.
Altitude and Azimuth of
flare
Flare position relative to digital horizon
No guess work now!
Display Explorer
Enable Reference Points
Move To
You can use the handy Orientation
| Move To feature to quickly center on the Iridium Flare coordinates as
well. This will save you from having to search for this particular spot in
that you are taken directly there. First MAKE SURE you have the correct
date, time, and location set to when the Flare occurs in the menu option
Data | Site Information!
Hint: You can
right mouse click on the main TheSky display and choose Move To from the
menu.
Use TheSky's
Orientation | MoveTo
Move to
the Horizon based coordinates
Check to see if you have the
Object Type "Reference Points" set to visible under the menu item
View | Filters. You also need to have your common labels turned on
under View | Labels Common Names. Since these objects are so
bright you only need to be looking in the general direction of the flare,
i.e. the constellation in which the flare occurs. You cannot miss
the bright ones. Make sure you are looking a little before the
predicted time so that you do not miss it. The estimated times for
the flash are extremely accurate!
If you wish to center the position where
the "flare" occurs connect to the telescope first, disable tracking, then
use the Slew button on the Move To Dialog. Now just sit back and
wait for the proper time. Using a wide field live video or even a
large CCD at prime focus you can easily image the event!
Enter horizon coordinates
Then choose Slew to
Find Satellite by
name
Or pick from the
list
HINT: There are times when
enabling the satellite's ID makes it much easier to see, especially when
using large fields of view. In addition to being able to
Find Satellites by name you can
label the moving objects on screen for easy identification.
View | Display Explorer
Check the labels you want!
* "Bird" a term used
for a satellite coined by Roger Mansfield |
