Saturday, 26 October 2013

A short update on GOCE, five days after engine cut-off

It is now five days ago that the ion engine of GOCE, the European Space Agency's 1-tonne Gravity field and steady-state Ocean Circulation Explorer scientific satellite (2009-013A), cut off after the satellite ran out of fuel. Originally orbiting at an average orbital altitude of 227.5 km, it is since coming down (see earlier post here). The diagrams below provide an update on the evolution of the orbit's apogee, perigee and Mean Motion (see also earlier post here for explanations) .

 click diagrams to enlarge


As I write this, the average orbital altitude has dropped over 8 km already since the ion engine shut down on October 21st. Yesterday afternoon (25 October) the average orbital altitude had already dropped below 220 km altitude, with the perigee now below 217 km (see first diagram above).

GOCE is currently losing altitude at a rate near 2 km per day. That rate will notably increase over the coming days, as GOCE will drop faster and faster.

It is too early yet to provide meaningful estimates of the re-entry date. My current prognosis (for which I used Alan Pickup's SatAna and SatEvo software) suggests a re-entry in the second week of November, but note that this date will probably shift to an earlier date over the coming week.

Currently, the satellite is still maintaining an attitude (orientation) that is optimizing for low drag. It does so using magnetic torques. At some point close to re-entry, that system will probably fail and GOCE will then lose attitude control. As it does so, drag will increase, which will seriously influence the re-entry date, shifting it to an earlier time. Meanwhile, the sun has been quite active the last few days, which speeds up the decay as well as the density of the Earth's outer atmosphere changes under the influence of solar activity. My very preliminary prognosis was made with an average forecast F10.7 cm solar flux of Fx=135 for the coming 20 days, but unexpected solar outbursts might alter the true picture.

I expect that several sources will start to provide re-entry estimates in the days before re-entry. The chief authoritive sources will be ESA itself, and the TIP-messages by USSTRATCOM on their  Space-Track portal (needs an account to access).  I expect that several independent analysts will provide re-entry estimates as well. The Aerospace Corporation provides re-entry estimates based on their own re-entry models, but is usually lagging behind. Their predictions sometimes strongly differ (up to several hours) from the final re-entry times and locations determined by USSTRATCOM (which I consider to be a more reliable and authoritive source).


(note: in the first diagram above, the values for perigee and apogee show some short-term fluctuation during the first 2-3 days after engine cut-off. These fluctuations are the result of errors in the orbit determinations, which easily occur (and are inevitable) when the data-arc used is still short and fitting error margins are hence wide. As the observational arc grows, the orbital determinations become more stable, which is indeed what we see over the last two days.
The apogee and perigee altitudes in the first diagram have been calculated from the values for Mean Motion and eccentricity using a fixed Earth radius of 6378 km, ignoring Earth's oblateness. Orbital elements are from USSTRATCOM (needs an account to access) with a secondary source (open access) here)
.

Note 31 Oct 2013: a new update here.

Tuesday, 22 October 2013

[Updated diagrams] GOCE is falling!

[diagrams updated 23 Oct 2013, 9:15 UT] 

GOCE, The European Space Agency's 1-tonne slick Gravity field and steady-state Ocean Circulation Explorer scientific satellite (2009-013A), is now truely coming down.



During the night of October 17-18, fuel reserves became so low that the pressure in GOCE's ion engine fuel system dropped below a critical 2.5 bar.  Next, between October 21.12 and 21.54, the ion engine stopped functioning, and as a result GOCE is now clearly losing altitude.

click diagrams [updated 23 Oct 9:15 UT]  to enlarge 

The first orbital determinations after the engine cut-off on October 21 are still inaccurate and as a result they are fluctuating, as the observational arc is still very short. But in the diagrams above, it can be clearly seen that the Mean Motion (the number of orbital revolutions per day that the satellite makes, i.e. how many times it circles the earth each day) jumps to much higher values. More orbital revolutions per day means that the orbit is getting smaller. The orbit getting smaller means the satellite is coming down.

This can be seen in the second diagram too. The apogee (the highest point in GOCE's slightly elliptical orbit) is steadily coming down since yesterday. The perigee (the lowest point in GOCE's slightly elliptical orbit) is dropping too.

GOCE's ion engine, when still working, provided a force countering the drag that the satellite experienced from the outer layers of the atmosphere in its low ~225 km orbit. As a result the drag parameter Bstar fluctuated around zero. When the ion engine cut out, the satellite suddenly experienced the full force of atmospheric drag. This can be seen in the lowermost diagram, which shows that the drag parameter Bstar made a strong jump to high positive values. The drag slows down the satellite, and as a result it drops in orbital altitude.

Over the coming days GOCE will rapidly lose altitude. So shortly after ion engine cut-off it is still too early to provide an accurate prediction about when it will truely re-enter and largely burn up: but as a ballpark figure this will happen somewhere between 2 to 3 weeks from now, somewhere during the first two weeks of November. In the days before re-entry, I will update re-entry forecasts on this blog.

Most of GOCE's one-tonne mass will burn up on re-entry, but some 250 kg (in many small fragments) might survive re-entry. At this point, it is still impossible to predict where (and when) these fragments may come down as that is dependant on many contributing factors, some of which are difficult to predict (e.g. the effect of fluctuating solar activity on the density gradient of the atmosphere). It will only be possible to predict this with some confidence in the final hours directly before re-entry.

Although the satellite is now without propulsion, its scientific sensors are still working. GOCE will continue to gather important scientific data on the Earth's gravity field until very shortly before its final demise.

The satellite controllers at ESOC have told me they have put the satellite in Fine Pointing Mode: a series of magnetic torques which react to the Earth's magnetic field keep the satellite stable in attitude (orientation), preventing it from tumbling, even though it has lost propulsion.

Since 2009, the GOCE satellite has gathered highly detailed data on the Earth's gravitational field and ocean surface heights.

Note: the apogee and perigee altitudes in the 2nd diagram were calculated with a fixed Earth radius of 6378 km, ignoring Earth oblateness

My last view of GOCE, an image taken on 29 September 2013 during a twilight pass over Leiden (click image to enlarge)

Saturday, 12 October 2013

Past and future of the KH-11 Keyhole/Evolved Enhanced CRYSTAL constellation (part 4)

In a number of previous posts from the last month (this one being the most pertinent one), I probed the changes to the KH-11 Keyhole/CRYSTAL optical reconnaissance satellite constellation over the past 8 years, aiming to predict what will happen now USA 245  has been added to the constellation on 28 August 2013 (launch NROL-65).

The previous analysis was focussed on the orbital planes of the satellites. In this fourth post in this series, I will take a look at other orbital parameters, such as apogee and perigee heights, eccentricity and mean motion.

West plane KeyHole/CRYSTAL satellites:
 USA 129: launched in 1996,
now in secondary West plane, 
probably soon to be de-orbited?
(imaged 28 Sep 2013)

 USA 186: launched in 2005,
soon to switch from primary West plane to 
secondary West plane?
(imaged  5 October 2013)

USA 245: launched 28 August 2013
into the primary West plane
(imaged 5 October 2013)

Let me first briefly summarize the previous analysis. In these I showed that the KH-11 constellation consists of two primary orbital planes separated by 48-50 degrees in RAAN. In addition, each primary orbital plane has an accompanying secondary orbital plane, 10 degrees more west for the West plane and 20 degrees more East for the East plane.

Satellites are initially launched into one of the primary planes, in their primary mission: after a couple of years, and after a replacement has been launched into the same orbital plane, they shift to the accompanying secondary plane, going from primary mission into secondary extended mission.

For example, USA 129 did this in 2006 after the launch of USA 186; and USA 161 did this in 2011 after the launch of USA 224. I pointed out that I expect USA 186 to do the same early 2014 following the recent launch of USA 245 into the West plane. I also expect USA 129 to be de-orbitted.

The graphic summaries given in that previous post, were these two images (see previous post for discussions):





Shifting from primary to secondary orbital planes is however not the only thing that happens. When we look at various orbital parameters, we can see other, accompanying patterns, notably in the apogee and perigee heights:



(click diagrams to enlarge)

(note: all the orbital parameters used in the diagrams above have been determined by Mike McCants from amateur observations, including mine).


New plane, lower apogee altitudes, and more circular orbit

For example: in the previous post on this topic it was discussed how USA 161 (2001-044A) in the East plane manoeuvred from the primary East plane to the secondary East plane late 2011 by changing its RAAN by 20 degrees (i.e., by rotating its line of apsides). This followed the launch of USA 224 (2011-002A) into the primary East plane, as a replacement for USA 161.

In the diagrams above, we can see that other orbital changes took effect as a result of the same series of manoeuvres. In addition to its orbital plane, USA 161 (blue dots in the diagrams) also changed its orbital eccentricity and its apogee and perigee heights. The apogee height was significantly lowered (which initially confused analysts at the time), from about 960 km to eventually about 390 km altitude. The perigee height was raised somewhat, from 310 km to 390 km altitude. The result is a much more circular orbit.

The inclination of the orbit was also changed, by about one degree. The reason for this can be seen in the lowermost diagram: with the changes in apogee and perigee altitudes, the orbital inclination had to be changed to make the resulting orbit sun-synchronous again.

In all, although much of this was accomplished within 6 months after the massive manoeuvre of late August 2011, it took USA 161 about a year to settle in its new orbit.


A repeat of an earlier case

Earlier, in 2006-2007, changes in the orbit of USA 129 (1996-072A) in the West plane can be seen to follow a somewhat similar pattern.

After the launch of USA 186 (2005-042A) into the primary West plane in 2005, USA 129, by that time already 10 years old and hence quite of age, moved to the secondary West plane by changing its RAAN by 10 degrees. Accompanying this move, is a change in perigee and apogee altitudes. The perigee is gently raised from about 280 km to eventually 310 km altitude. The apogee is lowered from about 1020-1030 km to eventually about 770 km altitude. The orbit becomes much more circular as a result.

With USA 129, this process took much longer than with USA 161 and the changes are less drastic. Yet the ideas behind them are clearly similar to what USA 161 did five years later: change orbital plane from primary to secondary plane, lower apogee significantly, raise perigee gently, and circularize the orbit (although not to the degree like USA 161 later did).

The more gentle approach taken by USA 129 in 2006-2007 compared to USA 161 in 2011-2012 might implicate either of these two scenarios:

(a) USA 129 had less fuel reserves left in 2006 than USA 161 had in 2011;
... or (and I prefer this explanation):
(b) it was anticipated in 2006 that the lifetime of  USA 129 needed to be prolonged untill well after the initial lifetime estimates, putting restrictions on fuel use for manoeuvres.

Remember: this is around the time the KH-11/CRYSTAL follow-up program, the FIA Optical program, entered delays and was next cancelled. So option (b) could well be the case.


What to expect?

Based on these past patterns, I expect USA 186 to do the following things by means of  a series of manoeuvres starting the first months of 2014:

1) change RAAN by 10 degrees (i.e. rotating its line of apsides), moving itself from the primary West plane into the secondary West plane (see previous post here);

2) drastically lower apogee (currently at about 1020 km) to about 390 km altitude;

3) gently raise perigee (currently at 260 km) to about 390 km altitude.;

4) circularize its orbit as a result of (2) and (3);

5) change inclination by about one degree to re-attain sun-synchronicity after the altered apogee and perigee altitudes.

These changes should take a few months and be completed towards the end of 2014. They will likely be initiated by a large manoeuvre early 2014 (in February or March likely).

As mentioned earlier I expect USA 129 to be de-orbited this winter or spring.


Why the apogee and perigee changes?

One question pertaining is: why these changes in perigee and notably apogee? Is a circular ~390 x 390 km orbit easier to maintain? Is there instead some operational reason behind this change in altitudes, in terms of desired track-repeat intervals or equipment performance (e.g. demands of image resolution)? If  so, why are similar changes not made to the orbits of the primary plane objects but only to the secondary plane, extended mission objects? I have no answers, and at best I can speculate from a few ideas I have. That is not for this blog, however.


This post benefitted from discussions with Ted Molczan and Cees Bassa. Interpretations and any errors theirin are mine.

Monday, 30 September 2013

A farewell to GOCE

In the past, I have observed ESA's gravity probe GOCE (2009-013A), the Gravity field and steady state Ocean Circulation Explorer, a number of times (e.g. here, here, here, here and here), usually as a rather faint object producing brighter specular flares near culmination.


 click image to enlarge


This weekend I tried again, spurred to do so by some people at ESA's ESOC in Darmstadt. The reason was that GOCE does not have much lifetime left. It's ion engine will run out of Xenon and cut-off somewhere mid- to end October, and the expectation is that the spacecraft will then re-enter and disintegrate in the atmosphere within 2 to 3 weeks. Some 250 kilo of the one-ton spacecraft might survive re-entry, divided over 50+ fragments.

The Goce orbit already had been brought down in November 2012: its orbital altitude currently is no  more than 225 km. As a result, it currently zips across the sky at high speed. Because of the low altitude, it is visible in twilight or very shortly after twilight only.

The image above shows GOCE over the roof of my home in Leiden center in deep evening twilight of  Sunday 29 September. It was visible with the naked eye, but only barely.

The image was shot with an EF 2.0/35mm lens and because of the bright twilight sky I used a short exposure of 2.5 seconds. The elevation of the spacecraft was around 40 degrees, passing east of me. The sky background shows stars in Andromeda: about halfway of the chimney and the GOCE trail you can see the fuzzy glow of M31, the Andromeda nebula.

I had also tried to image the spacecraft the evening before (Saturday the 28th), but Murphy struck. I was a bit late in checking for passes that day (in twilight already) and discovered that the only visible pass would happen within minutes of me checking for passes! So I ran outside, grabbed the camera, slammed it on the tripod, aimed it...and forgot to take off the lens-cap....

That particular pass, in a somewhat darker late-twilight sky and at a higher elevation through Cygnus, was a nice one, where GOCE was clearly visible to the naked eye. GOCE was racing through the sky, about the fastest you will ever see a satellite move in the sky. Quite apt for "the Ferrari among the satellites"!

This might have been my last view of GOCE ever: over the coming days the passes will become increasingly more unfavourable for my location.

It will be interesting to follow the satellite to decay once its engine has cut off. The ESOC people told me they will try to put it in a fine-pointing mode just before it does so, but there is a possibility that at one point it will lose attitude and will start tumbling.

Sunday, 29 September 2013

ISS and Cygnus

On September 18, Orbital Science Corporation launched an Antares rocket from Wallops, with the Cygnus COTS demo as payload. Just like SpaceX-es Dragon, the Cygnus is a commercial cargoship built to bring cargo to the ISS as part of  the Commercial Orbital Transportation Services (COTS) initiative. The September 28 launch is the inaugural demonstration flight of the Cygnus.

Initially Cygnus was to dock with the ISS on September 22nd, but a communication problem between the ISS and the Cygnus board computer caused a delay. Next the launch and docking of Soyuz TMA-10M bringing a new astronaut crew to the ISS on September 25 intervened, with the result that the Cygnus docking was rescheduled for September 29th.

click image to enlarge

In the early morning of September 29th, around 4:01 UT (6:01 am local time), ISS and the Cygnus COTS demo cargoship made a 40-degree pass in the southern sky as seen from Leiden. I had no idea how close the pair would be before actually observing the pass. It turned out to be close, the two spacecraft passing some 15 seconds after each other. The ISS was leading, Cygnus following.

Shortly after emerging from eclipse, the Cygnus was reasonably bright (mag. +3) and visible by the naked eye. But it quickly lost brightness, and by the time the pair entered the FOV of my camera, which I had aimed at Orion, Cygnus was no longer visible to the naked eye.

As a result, the image above (taken with an EF 2.0/35mm lens) is not the best: I had to pull a full suite of post-edit tricks to make the very faint trail of the Cygnus stand out a bit better. The image shows the pair traversing the area of Orion's belt and the Orion nebula.

Saturday, 28 September 2013

Hanging out with Astronauts: ESA/DLR's SocialSpace Cologne, 22 September 2013

(note: click the images with this post to get larger versions)

It can be safely said that unless you work in the space industry, you won't meet an astronaut very often. So you can perhaps imagine how exciting it is to the average space buff like me, to meet seven of them in one day!

Now hold that thought, and imagine how surreal the moment becomes when an astronaut (Léopold Eyharts, pictured below) is sitting at your table, in the chair right next to you, casually discussing the merits of the Soyuz versus the Space Shuttle in the same way that others compare a Volkswagen to a Prius...


Astronaut Léopold Eyharts sitting next to me at SocialSpace Cologne, discussing the merits of Soyuz versus Shuttle

That certainly is not your average Sunday afternoon....

The scene I describe happened in the afternoon of  Sunday 22 September at the SocialSpace Cologne meeting organized by the European Space Agency ESA and the German Aerospace organisation DLR.  The meeting took place at the DLR complex near Cologne, Germany.

SocialSpace is ESA's new name for a Space Tweetup, the new name reflecting that they seek an audience from a wider scope of their social media followers than just Twitter.

Until a year ago, when I attended my first, the 'tweetup' phenomena was completely unknown to me. Readers of my report on the May 2012 AndréTweetup at ESTEC will remember how I was unsure what to expect, half of me fearing that I would be confronted with 70 Sheldon Coopers plus a handful of Wolowitzes, dressed up in trekkie costumes...

(incidentally, there was a trekkie among the SocialSpace attendants this time, dressed up as Mrs Spock. Yes, Mrs Spock...: in stockings, and complete with pointy ears).

In reality, these tweetups turn out to be interesting and fun, the people involved generally quite sane and very nice, and an occasion where you make new friends. Some of these I now met again, in the context of this SocialSpace Cologne event, and I discovered that this proces of meeting attendants you know from a previous tweetup, together with the fact that you make a bunch of new like-minded acquaintances, is an important part of the social process of this kind of meetings. For example, I met Eico and Alex Neumann again (@Travelholic and @4tuneQkie on Twitter), even though they did not participate in the actual tweetup SocialSpace this time. They were however present at the informal social gathering at Brauhaus Sion the evening before the event.

SpaceKoelschX the evening before SocialSpace: 40 Space tweeps, beer and schnitzels

This unofficial pre-gathering called SpaceKoelschX consisted of some 40 people gathering for Kölsch (local beer), schnitzel, bratwurst, bratkartoffeln and a general swell time on the evening before the SocialSpace event. Most of them were SocialSpace attendants, and some of the ESA social media people were there as well. But the group also included people from previous tweetups that were not selected to attend this time, but came to Cologne on their own volition to visit the German Aerospace Day, a huge event which attracts about 100 000 visitors.

The ESA/DLR SocialSpace event itself took place the next day in a large tent on the vast DLR grounds bordering the airfield near Cologne, in the context of the already mentioned bi-annual German Aerospace Day.



two fish-eye views into the SocialSpace tent

The 60 attendants were selected from a large group of active social media followers who applied to a call spread through the ESA/DLR social media accounts (i.e., Twitter and Facebook). These lucky ones selected, including yours truely, got treated to a special program of lectures, a VIP tour through the DLR and ESA facilities, as well as a meet-and-greet with a whole bunch of astronauts.

And when I say "a whole bunch", I truely mean: a whole bunch. At a certain moment our SocialSpace tent on the DLR grounds started to teem with blue flight suits, to the point where I started to mutter: "we must find the nest and destroy the eggs!".

The image below shows you, from left to right: Reinhold Ewald, Thomas Pesquet, André Kuipers, Alexander Gerst, Frank de Winne, Léopold Eyharts and Andreas Mogensen:


Part of the tweetup SocialSpace tradition seems to be the presence of a number of mascots. I have covered Hugh the bear before in my report on a previous tweetup: present this time were a host of other mascottes, ranging from a Space Barbie to a Pink Little Dragon to Camilla the Space chicken. I must admit, this is a part of the Space tweetup SocialSpace folklore that I still have to get used to...

Me posing with Pink Little Dragon and Camilla the Space chicken

@projmgr and Space Barbie

@4tuneQkie with Camilla the Space Chicken and Pink Little Dragon during the SpaceKoelschX
ESA's Daniel Scuka (right) and another ESA employee who's name I do not know DLR's Elke Heinemann with Paxi, ESA's kids mascott. A life-sized version of Paxi visited us later.

While this all might make an impression of Space oddities, there was serious business as well. We got treated to a fine series of lectures that day by several ESA and DLR scientists, astronauts and a test pilot.

After we were picked up at Porz-Wahn station and brought to the venue by bus, the traditional handing out of badges, T-shirts and goody bags took place. After brief general introductions by the organizing team of ESA and DLR, we all shortly introduced ourselves. One of the nice things of large ESA tweetups like this is the very international vibe. The attendants to this SocialSpace came from all over Europe and even beyond, including the US and Canada.

Next we all set up shop with our laptops and other devices, from which we started to Live tweet the event. After all, it is a tweetup, n'est ce pas? We did it so well that #SocialSpace became a trending topic for a while. Two of the attendants even established a live webcast of the event.



The series of lectures started with ESA's Robert Meissner lecturing about the use of satellites for remote sensing. Apart from breathtaking satellite imagery, his lecture provided a good overview of the kind of remote sensing observations satellites can perform, and their practical application. Keeping an eye on crop production and soil and biomass degradation are important applications, for example.

Apart from modern imagery and their application, Meissner also showed us the very grainy first image of earth ever taken by a satellite, over 50 years ago. With a jump to the future, he announced that the GMES/Copernicus data, an ambitious Remote Sensing program by ESA, will be Open Access.


Sometimes satellite images contain baffling things. In the image above, Meissner shows us a giant geoglyph of the Egyptian god Horus that is visible on satellite images of an area in the interior of Australia. It was probably created as a joke by the Oz Army Corps.

The next lecture by Jens Danzeglocke connected to the previous lecture by taking a detailed look at the role European spacecraft (amongst others) play in disaster crisis management. The information exchange network the spacecraft play a role in, helps local authorities to quickly assess damage from natural disasters and coordinate disaster relief efforts based on these results. Most of these activities (about half of them) concern flood disasters, and Danzeglocke told us that radar satellites play an important role in these, as flooding disasters tend to be accompanied by cloud cover. The international Space charter the European space agencies take part in covered over 400 disasters in 110 countries since  2000.

Next another Jens, biologist Jens Hauslagen, lectured about "food in space". This was an interesting lecture about research into the useful application of waste recycling for crop growing in a closed system (e.g. a Space Station). Did you know that one human produces 10 kg of urea, 110 kg of 'organic waste' (that is: poo) and 100 kg of left-over food each year? In a closed system, these have to be recycled, and Hauslagen works on a series of very intricate ways to do this, including all kinds of filters but also small bio-organisms and even fish. Not only does this reduce waste: by recycling it enables the growth of food in long duration missions. His work has a down-to-earth application too: for example, there is a Maroccan town that recycles leftover waste from its fruit- and vegetable markets with techniques developed by Hauslagen and his team.

DLR test pilot Steffen Gemsa

The next speaker was DLR test pilot Steffen Gemsa. This is one of the pilots who took off in a research aircraft to fly into the volcanic ash cloud during the April 2010 Icelandic volcano crisis. Yes, you read that right: all over Europe aircraft were grounded, and this guy deliberately flew into the ash cloud. It's part of his job, that also includes testing aircraft under specific conditions, and conducting research flights with scientific equipment. It was an interesting lecture, as a result of which I learned the interesting bit of trivia that there are only five (5) test pilot schools worldwide.

Following Gemsa, Manuel Mezt and Holger Krag of ESA and DLR talked us up to date on all matters concerning Space Debris, ways to detect them and ways to mitigate the dangers of them. This included some results of simulations, and visualizations of all space debris in orbit around the Earth. Which is 93% of all objects currently in orbit.

Manuel Metz visualizing all object in orbit

Krag told us that every day some satellites are hit by (very) small particles of space debris smaller than 0.1 mm. The number of particles has dramatically grown over the past years due to a Chinese ASAT test in 2007 and a collision between an old Russian rocket booster and the Iridium 33 satellite in 2010. Krag made clear that if we continue this way, spaceflight will soon become impossible. Hence, measures are necessary to reduce the amount of space debris.

One way to reduce space debris is by making objects decay faster. This can be done for example by fitting spent rocket boosters and decommissioned satellites with solar sails. These sails increase drag, reducing on-orbit lifetimes.


 Krag: fitting satellites with solar sails after decommision will speed up their decay

Incidentally, Dutch astronaut (ehrm, pardon: European astronaut of Dutch origin) André Kuipers would later tell us about his experience with space debris too: during his stay on the ISS in 2012, they had to do two diversion manoeuvres plus a retreat into the Soyuz capsule because of close encounters with larger space debris.

After I asked a question in the discussion, Manuel Metz came over to me at the start of lunch, and told me he actually reads my blog. Wow!

Lunchtime also served as an hour off to freely roam the DLR grounds. Together with @Susivic I made a short visit to the airfield to see some of the aircraft there, including a Eurofighter:


Eurofighter, the jet our government did not buy

Incidentally, this was also the moment we first glimpsed André Kuipers, whom would later visit us in the tent.

When we came back from our short stroll over the DLR Open Day, DLR chairman and ESA director Jan Wörner and Thomas Reiter briefly took the stage.Whenever you see suits on stage, you know they will talk politics. Space politics in this case, with a brief discussion of future plans and goals. Reiter made the interesting statement that "I can believe we will perhaps see humans return to the surface of the moon in the next decade".

Next came a series of lectures all connected to ESA's Rosetta sampling mission to comet Churyumov-Gerasimenko. The first lecture, a grand overview of this exciting mission to land on a comet (!), was by project PI Gerhard Schwehm, who was involved when the mission was conceived in 1985 (!) and now will see it completed just before his retirement. In the original plans comet Wirtanen was the target, but when the launch suffered a  delay, comet Churyumov-Gerasimenko was selected.


 Schwehm

After Schwehm, and as an intermezzo, the astronaut and my fellow countryman André Kuipers took the stage, as a replacement for Samantha Cristoforetti who at the last minute could not make it.

I decided that the Geek code in this case as a rare exception does allow for a selfie:

Selfie with astronaut in the background

André told various anecdotes from his PromISSe mission in 2012 (the longest ESA mission onboard the ISS), including the short-circuit in the solar panels, the temporary retreat into the Soyuz because of a dangerously close encounter with a large piece of space debris, and the fact that all three of them threw up after their Soyuz capsule landed in the Kazachstan steppe. He told us astronauts need half a year to recover from a spaceflight and that the bone loss suffered during a long ISS stay might actually never fully recover. The unknown long-term effects of cosmic radiation are also a concern.

Kuipers stated he welcomes commercial spaceflight as long as it is done safely, and he said he believes the SpaceX Dragon will one day fly astronauts.

Kuipers was one of the two astronauts grappling and hooking up the first DragonX capsule to the ISS. Later that day, when the astronauts present intermingled with the SocialSpace attendants, he would tell the story of docking the Dragon in more detail:

St Kuipers, retelling how he slew the SpaceX Dragon in an epic heavenly battle

Stephan Ulamec and Koen Geurts next lectured on details of the Philae lander that is part of the Rosetta mission effort. Ulamec told us that since no-one has ever landed on a comet before and we actually know very little of the make-up of the nucleus of the comet in terms of surface condition and density, it is a very tricky thing to do. Another challenge is the long-term operation of the spacecraft without RTG's to provide energy (Rosetta/Philae has solar panels only).

The lander is actually washmachine sized and the landing will involve a bit of Space Whaling: the probe will fire two harpoons into the cometary nucleaus and rope itself in. Its first act will then be to take a 360 degree panorama to see in what position it landed. Ulamec succinctly summed up the scientific importance of the project by stating: "If you want to get to the pristine material, you will have to land there" (with "there" being the comet, which is made up of pristine materials from the formation of our solar system).

After these highly interesting lectures, it was time for our VIP tour through the EAC facilities. We were divided up in two groups, each of which  was met by an astronaut (in my group's case, Thomas Pesquet) who would act as our guide. Pesquet did not spare us the gory details: at the Neutral Buoyancy Facility, he told us astronauts frequently lose a fingernail while practising in the suit in what I am apparently not allowed to characterize as a giant swimming pool.

Columbus module mock-up in the EAC Neutral Buoyancy Facility
Apart from the Neutral Buoyancy Facility, we also got a quick glance at the only existing life-size mock-up of the ATV, which made me realize how big the ATV's actually are. Next, Pesquet took us to a place rarely visited by outsiders: ESA's  Eurocom control room, where they monitor and control all kinds of European things going on in the International Space Station:

Eurocom

 Thomas Pesquet explaining things in the Eurocom control room to us

Geek humor in Eurocom

After this first truely Close Encounter with an alien astronaut, we went back to the SocialSpace tent where we got a very cool demonstration by ESA's  Advanced Concepts Team, who work on some very geeky stuff. They demonstrated a quadcopter drone controlled by an iPad app, simulating the ISS in a game environment. The app might one day actually help finetuning techniques so drones (or spacecraft) can automatically assess distance.

the drone


Then it was time for more astronauts again. Alexander Gerst who had elsewhere just completed a press conference where he revealed the name of his upcoming ISS mission, Blue Dot, and Thomas Pesquet who earlier was our guide at  the EAC tour, took the stage.

 Thomas Pesquet (left) and Alexander Gerst (right)

They turned out to be a golden comedy duo, with very witty retorts between the two. Thomas Pesquet next asked the audience for suggestions what to do in terms of social media activities when he is in the ISS, "since about everything already has been done by now...". May I suggest a weekly comedy show from space perhaps?

Then the moment came where the tent suddenly started to teem with an overload of astronauts. Seven of them took the stage, and next intermingled with us by sitting down among us at the tables, answering questions and relating experiences. At this point, we had a significant part of the European astronaut corps hanging out with us!


 Léopold Eyharts, who went to MIR in a Soyuz in1998 and to the ISS in a Space Shuttle in 2008, sat down next to me and told us the ride up is better on the Soyuz, but the journey down is much more comfortable on a Shuttle. One of the reasons which he mentioned for that verdict was the constant swinging of the Soyuz capsule under the parachute.

Apart from listening to Léopold Eyharts, I listened to André Kuipers and later had the opportunity (thanks to Suzanne Pieterse (@Susivic), who handled the camera) to have my picture taken with him. He also signed a folder of postcards for me and my SocialSpace badge. Which made me tweet, in a Sheldon Cooper moment: "Now I have his DNA!"



André Kuipers kindly posing with me

signed badge and postcard folder


With this, the day finally ended. Or more or less: there was an informal drink afterwards, which saw more opportunity to talk to astronauts, various ESA people and other attendants.

ESA's Social Media guy, Daniel Scuka, talking to two attendants


Around 18:45 I left for the station for the ICE journey back, but not after grabbing a quick bite with Lynn van Rooijen (@lynnvr) at the trainstation. I was knackered when I arrived home, well after midnight: but it had been worth it. This was a cool day with an overload of astronauts, a highly interesting lecture program, and lots of very nice people. I would not have wanted to miss it!

I warmly want to thank the ESA/DLR organizers, and specifically Daniel Scuka, for inviting me to this wonderful day and all the good care they took of us.


(Note: photographs with this report were taken with two cameras: my Canon, and a rather old and decidedly less quality iPhone. So apologies for the bad quality of some of them)

Thursday, 26 September 2013

[UPDATED 2x] Visualizing the trajectory of the September 10 Trident missile test in the Atlantic

The past days I have covered the story about German astrophotographer Jan Hattenbach's September 10 strange photographic observations from La Palma on this blog. Along with Jonathan McDowell I quickly suspected this was a  missile test launched from a submarine in the Atlantic. This was later confirmed: Lockheed-Martin and the US Navy announced that it was a test with a Trident II D5 SLBM launched from a submerged Ohio-class submarine.

More information next emerged that contained some clues to the launch trajectory. Now Cees Bassa has done an extensive analysis, modelling a trajectory. The details can be found here on the Seesat-L mailing list. He finds a launch location near 28 N, 68 W, more to the west than I initially thought.

I used Cees' results on the launch location and STK to fit a ballistic trajectory through Cees' launch location and the probable target area discussed earlier. The trajectory (visualized below) fits well with the altitudes and azimuths as photographically observed by Jan Hattenbach from La Palma (see astrometry in the appendix to my post here).





click maps to enlarge

The trajectory STK fits allows to say something about altitudes and flight-times. The launch occurred near 21:10:40 UT. After a 36 minute flight over a distance of 8660 km, the target area between St. Helena and the Gabon/Congo coast was reached near 21:47:00 UT. In the top of its ballistic trajectory, the missile reached an altitude of 1800 1900 km.

(note added 27 Sep 2013, 13:00 UT : Cees Bassa has since released the detailed data of his ballistic curve fitting: he has the apogee somewhat lower, at 1650 km, and a flight time between 21:10:00 UT and 21:44:45 UT, one minute faster. Please note that the diagrams below are based on the STK derived trajectory I cobbled together, not Cees' data.

Update 28 sep 13:00 UT: Cees' trajectory does not have the impact point in the published exclusion zone, but somewhat to the East of it. That is the major cause of the discrepancy between the results Cees published, and the ballistic trajectory I present here, which does land squarely in the exclusion zone. With the impact point shifted slightly westwards, the apogee altitude shifts upward if one wants to match the azimuth/elevation data from La Palma.)



click diagrams to enlarge

The two events at 21:17:08 and 21:08:43 UT that I initially misidentified as the 2nd and 3rd stage ignitions, but which are, as Jonathan McDowell pointed out, likely the MIRV bus and MIRV separations, happened at 1130 and 1330 km altitude in the ascending phase, after 6.5 and 8 minutes of flight-time, 1860 respectively 2235 km from the launch location. They are marked in the diagram below:

click diagram to enlarge


(note: for this post I am much indebted to Cees Bassa and his fine analysis. His trajectory reconstruction provided the basis for the diagrams and the timing and altitude information in this post. Cees' own detailed trajectory data can be found here - they slightly differ from what I present above, but see the note elsewhere in the post above.)