Sunday, 31 August 2008

Purple volcanic twilights, and KeyHole satellites

Last Friday evening was clear again. Looking outside in twilight, I noted the sky was amazingly purple, due to volcanic aerosols spewn by the Kasatochi volcano in the Aleutians. I walked a few blocks to the Witte Singel canal and shot this picture, with one of the domes of Leiden Observatory silhoutetted in the far distance:

(click image to enlarge)



Later that evening, I captured two Keyholes, USA 129 (96-072A) and USA 186 (05-042A), the Japanese satellite IGS 1A which made a small manoeuvre recently, and a very fine mag -3 flare by Iridium 65. Unfortunately, clouds came in later in the evening.

(click image to enlarge)

Sunday, 24 August 2008

Asteroid 183294 Langbroek!

This weekend, I got notified of the fact that the Committee on mall Body Nomenclature of the International Astronomical Union (IAU) has decided that asteroid 183294 (also know by its temporary designation 2002 TB382) will henceforth be officially named:

183294 Langbroek

The citation text from Minor Planet Circular # 63643:

(183294) Langbroek = 2002 TB382
Discovered 2002 Oct. 9 by NEAT at Palomar.
Marco Langbroek (b. 1970) is a Dutch archeologist and amateur astronomer whose main interests lie in meteor astronomy. He is an avid meteor observer, active within the Dutch Meteor Society. The name was suggested by S. K├╝rti.

Asteroid 183294 Langbroek is a main belt asteroid with an estimated 2.5 km diameter (H 15.6), has it's perihelion at 2.69 AU, aphelion at 3.39 AU and an orbital inclination of 6.34 degrees. It revolves around the sun once each 5.3 years, between the orbits of Mars and Jupiter. It was discovered on images taken 9 October 2002 with the 1.2 meter Schmidt telescope of the NEAT program at Mt. Palomar.

I feel very honoured by this asteroid naming.

Here's a blink of the discovery triplet, made on 9 Oktober 2002 with the NEAT 1.2m Schmidt telescope at Mt. Palomar:



Below is a plot of the orbit:

(click image to enlarge)


For an interactive orbit plot (JPL website), click here.

Lacrosses and a very fine USA 161 flare

Coming back from a date shortly after midnight of August 23-24, I noted it was very clear, with only occasional small cloud fields passing. This allowed me to photographically target the optical imaging Keyhole satellite USA 161 (01-044A) and the radar Lacrosses 4 & 5 (00-047A & 05-016A).

USA 161 briefly brightened in Cassiopia, featuring a very short mag. 0 flare at 23:44:09 UTC. I was so lucky to have the camera open at that time, resulting in this very fine flare picture (with below it, the brightness profile):

(click images to enlarge)


Friday, 22 August 2008

More on the USA 193 shootdown

The online Bulletin of the Atomic Scientists has published an essay by Harvard astrophysicist Yousaf Butt with a very critical view of the official reasons given for the USA 193 shootdown.

Butt filled a request through the Freedom of Information Act and obtained the report featuring the re-entry model and analysis that was used. And found it to be flawed and on closer look not quite supportive of the alledged 'danger' of the re-entry of USA 193's hydrazine fuel tank.

The report is very cautious and it's authors already note that some of the model assumptions are not realistic. Importantly, it shows that even with these assumptions maintained, much of the tank's titanium outer layer will ablate according to the model (remember how Oberg denied this in his essay?!), leaving only a very thin outer shell 1/5th or less of the original thickness. This assumes uniform ablation (which is not realistic).

Butt argues that when more realistic assumptions are made, this suggests the tank would likely have been destroyed upon reentry.

You can read the essay here, and it includes a link to the report pdf.

The essay highlights:

  • A NASA study on the survivability of USA-193's hydrazine fuel tank used an oversimplified model, leading to an overly optimistic assessment of the tank's survival.
  • But even this study showed how the tank would have burned up when reentering the atmosphere.
  • Therefore, Washington's contention that the tank would have hit the ground intact, posing a health hazard, seems questionable.
Another thing to note is that the tank was not completely filled with fuel, but 76% filled. This turns out to be of importance in assessing the fate of the tank.


(with thanks to John Locker for te 'heads up')

Wednesday, 20 August 2008

IGS 1B and NOSS 3-2 amidst flying clouds

Yesterday evening the atmosphere was very dynamic, with flying clouds. I did manage to capture the NOSS 3-2 pair (03-054A & C) in twilight, and IGS 1B (03-009B). The NOSS image suffered from twilight and clouds, but also yielded a fast stray (which I still have to identify).

IGS 1B was very bright again (+0.5) when it came out of eclipse and passed almost overhead. The picture below gives a good indication of the observing conditions.

(click image to enlarge)

Sunday, 17 August 2008

Keyhole USA 186 manoeuvred at Aug 14.6, and imaging a NOSS duo (REVISED)

A late report on my August 14 observations and associated topics.

August 14 featured a nice clear evening. I captured the Keyhole USA 186 (05-042A), the Japanese failed radar sat IGS 1B (03-009B), the NOSS 3-2 duo (03-054A & 03-054C) and a piece of a Russian rocket stage (86-052D) that I caught as a bright stray.

This is the first time that I managed to get a good image of a NOSS pair. I snatched them close to the zenith, while traversing close to Vega. They show up surprisingly well in the image:

(click image to enlarge)



NOSS (Naval Ocean Surveillance System) satellites operate in pairs or triples (the older ones), orbiting close together, and locate shipping by tracking radio communications. They belong to the US Navy. Usually they are faint (mag. +5 to +6) but on occasion can appear brighter.



USA 186 Keyhole manoeuvred: connected to Georgia events or not?

USA 186 (05-042A) appeared somewhat late, but as the elset I had available was 10 days old I did not think anything particular about that. It was Pierre, who observed the same pass from France, who realized the sat had made a manoeuvre. This was confirmed by additional observations the next two nights by Pierre, Ted and Alberto.

Below is the image taken by me, showing USA 186 crossing close to M13 in Hercules:

(click image to enlarge)



The manoeuvre entailed adjusting the eccentricity and mean motion, and perhaps a small inclination adjustment. Perigee was brought down slightly, and apogee up, to a 261 x 1024 km orbit (was 264 x 1017 km).

Using a pre-manoeuvre elset by Mike and an adjusted version of Ted's post-manoeuvre elset, I find that the manoeuvre likely happend at Aug 14.6 UTC, some six hours before Pierre and my observation.

Satellites usually manoeuvre when the perigee is at the equator, as this minimizes fuell needed and maximizes results that can be obtained. USA 186 did not have it's perigee on the equator on the moment of manoeuvre however.

The manoeuvre comes at a time when chaotic war activities between Russia and Georgia are a focus of interest. This opens the question whether this manoeuvre of USA 186 (a Keyhole/improved Crystal satellite with high definition optical imagery capacities) is related.

Checking the pre-manoeuvre orbit against the post-manoeuvre orbit concerning passes over the relevant area of interest, it appears that the object was to synchronize passes as much as possible into a sequence where a daylight pass is followed exactly 11 hours later by a nighttime pass: with in addition an as exact as possible repeat of the observing geometry after 4 days. Whether or not this is related to the Georgia events, is a matter of speculation. Ted thinks it is not the case.

The patterning is apparent from this table (times are in UTC) showing passes over/near Georgia:

date____old orb___new orb
(2008)___pass______pass
-------------------------
15-8____06:58_____06:58

15-8____17:57_____17:58


16-8____07:22_____07:22

16-8____18:21_____18:22


17-8____06:08_____06:09

17-8____17:06_____17:09


18-8____06:32_____06:34

18-8____17:30_____17:34


19-8____06:55_____06:59

19-8____17:54_____17:58


20-8____07:19_____07:23

20-8____18:17_____18:22

------------------------


Daylight pass followed 11 hours later by nighttime pass (click images to enlarge)


Wednesday, 13 August 2008

IGS 1B flare, no Perseids

Yesterday was a strange evening. The day had been very clear, but with very strong wind (with gusts up to 100 km/h). In twilight, some clouds came in. It then got completely clouded, cleared again, and finally got clouded again, including a thunderstorm.

This all made me miss the Perseid meteor maximum. During the clearings however, I did manage to catch Lacrosse 2 (91-107A, in twilight), and the failed Japanese satellite IGS 1B (03-009B).

The latter was very bright (about +0.5) in the southeast and east. It then faded notably to +3, +3.5 just past east, and finally flared brightly to -1.5 in the northeast around 21:03:55 UTC.

I got three images of both satellites, totalling 11 positions (I dropped the faint trail end of the third IGS 1B image). The three IGS 1B images showed a second, very faint trail as well, which turned out to be the classified research MSX satellite (96-024A).

(click images to enlarge)


Tuesday, 12 August 2008

Oberg on the USA 193 shootdown

The renowned veteran space journalist and former mission control engineer James Oberg has published another article about the reasons for the USA 193 shootdown in february (see my detailed coverage of the USA 193 saga here).

Like in an earlier article, Oberg is strongly opposing suggestions that there is more to this all than the official reason given for the shootdown - the danger of the tank with Hydrazine reaching earth intact. He argues that that reason given was the true and sole reason.

As much as I respect Oberg, I am still not convinced (but then, I am merely only what Oberg calls an "amateur specialist". I observe satellites and determine their orbits. I do not launch them).

First, about disintegration of the satellite. Oberg makes an argument from a comparison with meteorite falls. That argument, at least in the way he presents it, is flawed.

Oberg argues - and he is correct in this!- that it is a widespread misunderstanding that meteorites arrive on earth surface 'red hot'. He points out that in fact they are cool when reaching earth surface, and then tries to argue that they do not heat up during their fall:

Though a thin outer layer is briefly exposed to very hot air, for most of the descent that air is thinner than the purest vacuum inside thermal-shielding thermos bottles.

Now he is correct in this: small meteorites indeed arrive cold on earth surface, and of the object which does reach earth surface, only a thin outer layer has been heated.

But this is only part of the story, and as such the meteorite analogy is a very poor one.

There are two reasons why meteorites arrive cold on Earth. One is that from 25 km altitude, after being slowed down by the atmosphere to subsonic speeds, they stop ablating and enter a free fall that takes minutes to complete. During this phase they cool, much like the air the ventilator in your pc blows over your computer CPU cools your CPU.

A more important factor however is that heat generated during the incandescent phase of a meteorite fall, the result of atmospheric friction when the object still has cosmic speeds, is carried away immediately with the ablating material. It is for this reason that heat generated does not transfer much into the meteorite. This is basically what Oberg points out, but he neglects to tell something which is quite relevant:

that in this process of meteorite ablation, at least 70% (and usually more) of the meteorite ablates and hence vanishes. What reaches earth surface is at best 20-30% of the original mass.


The implications for the USA 193 tank, if we properly use the meteorite analogy, is therefore this. Either one of these two things will happen:

1) over 70% of the tank mass ablates and at best 20-30% and probably less of the original tank mass will reach earth surface;

Oberg however argues specifically against the notion of the tank being destroyed by ablation. The alternative option which remains then is:

2) the tank, due to it's special construction, does not ablate. In that case however, the heat dissipation mechanism Oberg brings up in his meteorite fall comparison will be absent too. In other words: the tank will heat up in its interior, unlike a meteorite.

In this case, Oberg's analogy is flawed.

Now, if I understand Oberg's article correctly, modelling (and who am I to question this) of the USA 193 tank entry would have nevertheless suggested the frozen hydrazine to remain intact.

In that case, you can actually question what the real danger is of a solid chunk of hydrazine ice contained in a metal casing reaching earth surface. It will only be dangerous when someone directly handles it (but even then).

Here, we should realize that tanks with -unfrozen!- hydrazine fly through our airspace daily. Most fighter jets contain a tank with hydrazine as an emergency fuel backup. The effects of this falling down on you will not much differ from those of the USA 193 tank falling down on you. Such crashes are not rare. For example, our relatively modest Dutch airforce lost 32 of its F16 fighters, which carry a hydrazine tank, through flight crashes. Some of these aircraft came down in populated areas (one actually hit a house).

All commercial aircraft carry tanks with fuel too - not hydrazine, but still not pleasant stuff. Chances that one of these tanks will descend on your head - and this happens from time to time- are much larger than that the tank of USA 193 would have. And we don't quite bother about that. So why bother about the USA 193 tank then?

USA 193 was not the first failed fuel-carrying satellite to fall back to earth in an uncontrolled way. Nor will it be the last. In fact, launch failures where final rocket stages fail to fire are common. It will be interesting to see whether future cases will get a similar treatment.

In my opinion, the USA 193 shootdown was done for multiple reasons, and the "danger" of the hydrazine tank is only one of these. It is a convenient one to defend the exercise to outsiders, but not the only reason.

I am quite convinced that other reasons were of equal or even paramount importance in making the decision:
- that USA 193 presented a very convenient target for a practical test of ASAT capabilities (thus also making the money spent on the satellite at least partly pay off);
- that it would prevent new experimental technology falling (literally) into wrong hands;
- and that it was a timely moment to remind China, the US Senate and Congress and the US public that the USA has ASAT capabilities too and that the technology in a wider sense (missile defense) was worth further funding. Note that in April 2008, barely two montsh after the USA 193 intercept, the US Congress re-examined the status of missile defense of which the used Aegis system is part.


Note: considering the USA 193 shootdown, John Locker's summary and the links he provide are worthwhile reading

Saturday, 2 August 2008

Milky Way photograph, and a tale of lens covers...

Yesterday was one of those occasions... The evening was beautifully clear here. The passes of KH's USA 129 and 186 were too much in twilight (I did see USA 186 visually though, but got no points) and I tried to photograph a pass of IGS 1B half an hour later, using my new Tamron Di II AF 17-50/2.8 lens.

The Tamron lens needs to be focussed using the "live view" function of my camera (Canon EOS 450D), as it has no "hard stop" at infinity, like most modern lenses.

I ran into trouble though. Pointed it to Arcturus but no star to be seen on the screen whatever I tried. Dito with Vega, Deneb. Frustration! Then worry. Was my camera malfunctioning?!?

I looked up. And saw a bright IGS 1B majestically sail accross the sky. Grrr!

I took the camera again. And then the quarter finally fel....

Yep: forgotten to take off the lens cover....

* bangs head against desk repeatedly *

Later that evening I made a series of images with the 450D camera + Tamron lens piggyback on my ETX-70 telescope. 69 frames of 10 second exposure each at 800 ISO and 17mm/F2.8 were stacked into this image of the Milky Way in Cygnus, mimicking a 11.5 minute exposure:

(click image to enlarge)


Difficult to believe for me too that this was obtained right from a town center, but nevertheless it is true! Stacking large numbers of short exposure images makes this possible.

Friday, 1 August 2008

Results on the partial solar eclipse (UPDATED TWICE)

I could follow the entire partial solar eclipse this morning: the sky was clear, but with periodic fields of cumuli passing.

I made a series of photographs of the event through my Meade ETX-70. Below a first result, taken around local maximum of the eclipse (11:25 CEST, 09:25 UTC). Exposure 1/100s.


(click image to enlarge)


Here is a full series covering the eclipse, taken at approximately 10 minute intervals (except near first and last contact):

(click image to enlarge)


And here is a time-lapse movie made from the images: