No observing opportunities

Last week for various reasons saw no observing opportunities. Either weather was bad, or I had other things to do.

This is a bad season anyway: from late September to January, and especially October-November, skies are often overcast.

Delta t deviation

It appears that my delta T values again come out
some ~0.3s "early" relative to other stations.

As this was not the case for my August data, I have
begun to suspect it is the result of my recent
change in camera settings (other setting for colour
and contrast, to bring out fainter trails better).
Apparently, this also changed the intitiation time
of the camera by an extra 0.3s.

As of now I will use the empirical 0.3s value to
adjust my timings accordingly.

USA 129, but no aurora

Monday, September 12, 2005, 23:59:46 LT

An aurora warning was out, as the geomagnetic
activity was very high due to a series of X-class
flares on the sun today and yesterday.

Aurora was not seen, but Keyhole satellite USA 129
(96-072A, #24680) was captured by the camera at
20:43:10 UTC. A clear unambiguous trail is visible
on the image, yielding two points. I am very curious
as to how the delta T values will compare to those
of other stations this time. It will be running "early"
anyway because of the high geomagnetic activity (which
increases the drag, as the atmosphere expands due to
it).

An exposure was made one minute earlier too, but the
satellite is not visible on that image.

Accuracy problem with deltaT

I posted a number of accuracy test lately. But now some
results have appeared that deviate. It concerns the data
on 96-072A (USA 129) of the 8th.

The problem is in the delta T values. They come out some
0.3-0.5s too early compared to other data gathered by
other stations around that time. It concerns data from
two separate images.

In below table, the asterisk-marked points are mine. The
other points are by David Brierley and Peter Wakelin.
The given delta T values are relative to Ted Molczan's
elset 05253.13803400.

deltaT
-0.10
-0.11
-0.37 *
-0.29 *
-0.48 *
0.04
0.06
0.07
0.07
0.08
0.11
0.05
0.10
-0.02
-0.11
-0.08
-0.03
-0.03
-0.03
-0.03
0.04

I am at a loss to explain this deviation.
Something in the timing is not right, but what?

The crosstrack value of the second point initially was
somewhat off (0.07 degree). This turned out to be because
I had switched the image reference time and object position
time in Astrorecord. When this was corrected, the crosstrack
value came out fine (but the delta T difference remained).

Flare of USA 129 Keyhole satellite

Yesterday evening I captured this image of the American Keyhole imaging satellite USA 129 (96-072A, #24680) starting to flare brightly near the zenith. A few seconds after the end of this exposure it reached magnitude -1.5. A second exposure starting 30 seconds later only shows a faint trail, estimated about magnitude +3.0.

This picture and the second one provided three positions

Another bright flare of Lacrosse 4 - imaged this time!

2005-09-05, 23:40 LT

During its deep twilight pass of 19:14 UTC (21:14 local time) Lacrosse 4 (00-047A, # 26473) showed a bright Iridium-like flare, just like two days ago.

The sky was still bright blue with only the brighter stars visible. Yet Lacrosse 4 stood out well for severall seconds. I estimate it reached at least magnitude 0.

This time, the camera was open when it happened. Nothwithstanding a light blue brackground, the flare is well-visible on the image. Stars from delphinus can be recognized at lower right.

Insomnia, Lacrosse 4 and a failed attempt for Lacrosse 5rk

Last night I could not get into sleep, even though I
tried hard. I hope this is not a return of the insomnia
that plagued me for months, untill a month ago I was
finally able to stop with sleeping medication.

As I was still awake at 4:30 am local time, I decided to
bring out the camera and target Lacrosse 4 (00-047A),
who made a pass around 5:08 am, the end of which was just
visible for me low in the east.

The winter constellations were rising this early in the
morning: the Pleiades and Mars shone brightly high in the
sky. Lacrosse 4 moved on the Auriga-Gemini border as it
cleared the edge of the house in the alley gap between my
house and the bank building opposite me. I captured a faint
but measurable trail.

A few minutes later I tried to target the Lacrosse 5rk
(the rocket that launched Lacrosse 5), but failed to
see it both visually and on the photograph.

Here is one of the two images of ISS I shot yesterday. It is moving below Lyra into Cygnus here. The bright star in the top is Wega (alpha Lyra).

Encouraging accurracy test using ISS

I've been doing some accuracy tests lately to check
on the accuracy of my experimental photographic camera
setup, as I am always striving for improvement.

After comparing some of my datapoints with data by others
on the same satellites earlier (see earlier blog entries),
I took advantage of the current start of nice and favourable
ISS evening passes to use ISS as a test target and compare
obtained positions to an accurate ISS TLE.

I obtained 4 positions from 2 images for ISS during last
evenings 19:55 UTC pass: two (the first two) with ISS in
the zenith, two with ISS going into eclips low in the
southeast.

25544 98 067A 4352 F 20050904195525800 17 75 1900355+263390
25544 98 067A 4352 F 20050904195536500 17 75 1952060+282850
25544 98 067A 4352 F 20050904195635800 17 75 2321209+227230
25544 98 067A 4352 F 20050904195646500 17 75 2339494+210810

Using Scott Campbell's SatFit I compared them to an accurate
TLE for epoch 05247.96166413

The result is as follows:

AZ EL ASP XTRK deltaT Perr
( 1) 184.50 64.32 83.18 0.02 -0.02 0.028
( 2) 157.31 65.03 94.14 0.01 -0.02 0.027
( 3) 96.58 34.40 137.74 0.00 -0.06 0.032
( 4) 94.09 30.36 141.68 0.03 0.17 0.091

sum 0.05184

Of course I was very happy with this result. When I use
the TLE issued previous to the above one (05247.68884259),
I get:

AZ EL ASP XTRK deltaT Perr
( 1) 184.50 64.32 83.17 0.03 0.18 0.204
( 2) 157.31 65.03 94.12 0.03 0.18 0.205
( 3) 96.58 34.40 137.73 0.00 0.13 0.067
( 4) 94.09 30.36 141.66 0.03 0.37 0.171

sum 0.17140

...and the truth will be somewhere inbetween I guess.

The 4th point merits some comment, as it clearly deviates
in the series. The reason is that the 4th point was
obtained while ISS was going into eclips fast. Instead of
being the true end of the trail due to the end of the
exposure (the reference time for this point), it probably
is the point where ISS crossed the imaging threshold of the
camera while fading out. Hence it being "too late" compared
to the other points.

I've been thinking about the pittfals of my system, and
the obvious one is pointed out by point 4 in the above series.
A start- or endpoint of a trail is not reliable when it is
not marking the start or end of the exposure, but the point
where the brightness of the satellite crosses the imaging
threshold, the trail limiting magnitude of the camera. This can
happen when the sat fades in or fades out (or both) or is faint
and irregular in brightness. When that is the case, it should
translate in a first point that is apparently "too early",
and/or a second point that is apparently "too late". Whenever
such things are visible in my data compared to other datapoints,
this is probably the reason.

But for a bright sat not near eclips, this ISS test again
suggests the digital camera system performs quite well.

So far this little, encouraging test. Hereby, I also want to
thank Scott Campbell for making available his software.

Update

Earlier today I wrote:

"Some 10-15 minutes before Lacrosse 4 I saw a nive bright
sat of about magnitude -1 to -2 low in the sky descending
to the southeast."

Of course, this was ISS.....

Flare of Lacrosse 4 (00-047A)

Targeted Lacrosse 4 (00-047A, #26473) again this evening.
Observing conditions were poor, the skies were hazy. Some
10-15 minutes before Lacrosse 4 I saw a nive bright sat
of about magnitude -1 to -2 low in the sky descending
to the southeast.

Lacrosse 4 made an Iridium-like flare, something which I
have not seen a Lacrosse do before. Starting at about
magnitude +2.5 when I started the exposure, it brightened
and gave a brief flare of about magnitude +0.5 some 10
seconds after the end of the exposure. The onset of this
was just captured on the image, the end tip of the trail
on the exposure is suddenly bright and fat.

This last point is some 0.2 seconds late relative to elset
05245.92208782

A Keyhole and ENVISAT, and NEA's

Thursday, September 01, 2005, 17:09:02 LT

Worked last night (31 Aug) with the camera in the new
colour/contrast setting. Images come out more dull now,
but I do have the distinct impression that faint trails
do show up better.

Catched USA 129 (96-072A, #24680), a Keyhole optical
imaging satellite with a decimeter resolution capability.
Faint trail but the measured positions come out fine.

Also catched a sat I initially could not identify. IDSat
gave no clear match. Ted Molczan then identified it as
ENVISAT. It puzzled me that IDSat did not gave me that
match, untill the solution jumped to me this morning
while I was commuting in the bus: a sign error in my
location's longitude? Indeed, a check when back home showed
this to be the case...

Spacewatch resumed operation again a few days ago, so the
mornings that I am at home are filled with hunting NEA's
again...

And after a series of clear nights, it is raining again...

Another accuracy test

Another test of accuracy: the plots show my positions for Lacrosse 4 (00-047A, #26473) obtained last night, along with positions obtained by stations 433 and 2018. The red dots are my data. The data are compared to Mike McCants elset 05420.93550308.

Station 433 uses a LL video camera, and 2018 uses stopwatch and binoculars if I am not mistaken. Note that with regard to delta T, the values should regres from negative values (satelllite early with respect to the elset) before the elset epoch to increasingly positive values (satellite late with repsect to the elset) after the elset epoch (which indeed they do).

Again, my setup seems to perform well.

Lacrosse 4

Wednesday, August 31, 2005, 00:27:31 LT

Slightly hazy, but reasonable conditions this evening.

Obtained two instead of one images of 00-047A (Lacrosse 4)
spaced 1 minute apart as it traversed Pegasus, and hence 4
points. The second pic shows the typical orange colour of the
Lacrosse satellites, due to orange metal foil covering, rather
well. The sat seemed some 0.15 seconds late relative to elset
05240.93550308

I might give Lacrosse 3 a try later tonight as well, if my
alarm clock cooperates. Yesterday it did not and I woke up 30
minutes too late....

Experimenting with a slightly different camera setting today
(other color/contrast setting). I have some idea that trails come
out better as a result.

Accuracy test - seem to do fine

Using data reported for Lacrosse 2 (91-017A, #21147) by stations 2018, 2675, 2701, 2751 and me (4352) over the past week, I analysed the accuracy of the positions relative to Mike McCants' Elset 05234.83672363, using Scott Cambell's SatFit program. The goal was to see how my own data accuracy fitted with the other stations, thus getting an indication of the performance of the setup here.

Above diagrams give the comparisons in terms of positional error, cross-track error, and timing error. Note that with regard to the error, "early" observations (those before the Aug 22 epoch date of the Elset should come out early (negative delta T), and "late" observations late (positive delta T). My station's data are shown as red dots.

Looking at the diagrams, my setup seems to perform well and I don't need to worry. Which is good to know...

Cirrus, and satellites

24 Aug 2005, 01:55 LT

Above picture is the Japanese spysat IGS 1B (03-009B, #27699) coming out of the earth shadow almost in the zenith, around 23:28:07 local time (21:28:07 UTC) this night. I saw it visually, coming out of eclipse and brightening rapidly to about mag +2.0.

Above picture resulted in a good position measured from the end point of the trail.

Conditions were rather poor this night. A pass of Lacrosse 2 (USA, 91-017A, #21147) suffered from fields of thin cirrus. The start of the trail was too ambiguous to measure, the end did yield one point.

Just like yesterday, the bank building opposite me had all the bright lights in their offices on: this while these offices were completely deserted.... This was a big nuisance, apart from being a waste of energy. I hope this is not going to be a new trend. being in the midst of a ciy allready is hard enough concerning the light pollution, and this is definitely notably decreasing my visual limiting magnitude. I have to shield my eyes against the glare!

Further analysis 91-017A (Lacrosse 2) data

Because the residual for my second point for 91-017A
of last night worried me, I ran SatFit again but this
time also incorporating my data of 17 August. These
are the results:

AZ EL ASP XTRK deltaT Perr
(1) 97.49 47.14 118.26 0.02 0.04 0.030
(2) 102.25 44.06 122.20 0.00 -0.08 0.032
(3) 91.14 49.19 114.34 0.01 0.03 0.016
(4) 96.63 46.27 118.46 0.01 0.18 0.082

Again deltaT of the last point of last night clearly
stands out. However, the results for 17 August do not
indicate this is something recurrent. Hence, it appears
the last point for last night is just anomalous. Such
can happen, it are observational data after all, which
always can have errors introduced by God-Knows-What.

Nice bright sat (Lacrosse 2)

Yesterday evening was clear (it is clouded again now),
and I catched Lacrosse 2 (#21147, 91-017A) making a very
nice pass over the rising Pegasus square at a steady
mag +2. The sat was seen visually, and the trail shows
up well on the image too. The startpoint measured was
very close to the last TLE for 21147, 05232.87066994,
the endpoint is off by some 0.15 seconds. The fit is
as follows (using Scott Campbell's SatFit):

AZ EL ASP XTRK deltaT Perr
( 1) 91.14 49.19 114.34 0.01 0.03 0.016
( 2) 96.63 46.27 118.46 0.01 0.18 0.082

Maybe this indicates there stil is some slight calibration
problem with regard to the exposure duration of the camera.

Some pictures of the equipment

Here are some webcam pictures of the equipment of Cospar station 4352 Leiden, the actual SatTrackCam. See also my detailed SatTrackCam website.

As you can see it is actually quite simple: a lap-top, a Canon Digital Ixus 400 digital camera, and (not shown here) a DCF77 radio controlled clock for accurate time keeping. The station's geographic coördinates have been obtained by GPS.

Another clear night: nice pass of Lacrosse 2

Thursday, August 18, 2005, 02:05:36 LT

A second clear night, with somewhat better sky conditions
than yesterday. Targets were the American Radar
reconnaissance satellite Lacrosse 2, and the Japanese
optical satellite IGS-1A that was also targeted yesterday.
Tried to capture USA 129 as well and indeed have a very
faint trail on the image, but too indistinct to measure
reliably. The limiting magnitude for satellites clearly is
near +3.0 for this camera setup.

Obtained two points for Lacrossse 2 and only one point for
2003-009A (IGS 1A), the start of the trail, as the end seems
to fade away and is very indistinct on the image.

By contrast, the trail for Lacrosse 2 is fat and bright. Saw
the sat make his pass visually, magnitude steady near +2.5 through
Pegasus just before entering the earth's shadow.