Hayabusa2

In 2014 I have published several posts about Rosetta, the spacecraft that has explored the comet 67P. Click here for my reports. I am very interested in these Close Encounters between spacecraft and celestial bodies. Here is a new one, the Japanese Hayabusa mission. Actually there are two Hayabusa spacecrafts, the first one was launched in 2003, the second one in 2014.

Their mission was basically the same: Fly to an asteroid,  land on it, collect some asteroid material, then fly back to Earth to deliver the collected material.  An ambitious project!

Hayabusa was the first spacecraft ever that has landed on an asteroid and returned to earth with some asteroid material. Not as much as was hoped for, because the mission encountered quite a few technical problems. Therefore a second, improved Hayabusa2 spacecraft, was designed and launched on 3 December 2014.

Here is an artist impression of the Hayabusa2. The boxlike spacecraft has dimensions of 1 x 1.6 x 1.25 m and a mass of 609 kg

Destination? A tiny asteroid, 1999 JU3.. In an earlier post I have explained the complicated naming of the minor planets. The J stands for the first half of May, U stands for 20 and the subscript 3 means 3×25. So this asteroid was the 95th minor planet, discovered in the first half of May 1999. This provisional name is replaced by a number and sometimes a name, in this case 162173 Ryugu. It is the 162173th minor planet and the name has been suggested by JAXA, the Japanese counterpart of NASA.

Here is the route followed by Hayabusa2 to Ryugu.The Earth orbit in blue, Ryugu in green and the Hayabusa2 in purple.

It reached the asteroid, 3.5 year after the launch,  on 27 June 2018, . One day earlier it took this picture of Ryugu, from a distance of about 40 km

Properties of Ryugu:  not really spherical, diamond-shaped, a diameter of ~ 900 m and a rotation period  of 7.6 hours. The gravitation at its surface is about 80.000 times smaller than on Earth!

Until December 2019 Hayabusa2 will stay near Ryugu, at a distance of 20 km (HP, home position), where the gravitational attraction of the asteroid is almost nothing.  From there it will investigate the properties of the asteroid and several times it will descend for a short time to the asteroid.

On 20 September the spacecraft started a slow, controlled descent and one day later, 55 m above the surface of Ryugu, it dropped two Minerva rovers. While they were falling down to the surface, Hayabusa2 ascended to HP. Both rovers are working correctly, a huge relief for the scientist,  They are really tiny, diameter 18cm, height 7 cm, mass 1.1 kg Here is an artist impression.

Both rovers have multiple cameras and temperature sensors on board They can move around by “hopping” and do this autonomously! Wheels like for example the Mars rover has, would not work in this low gravity world.  One hop can take 15 minutes and move the rover horizontally ~15 m.

This is a picture of the Ryugu surface, taken by  one of the rovers.The scientists are surprised that the surface is so rough.

On 3 October, the spacecraft descended again to Ryugu, to drop the MASCOT lander, developed by the German and French space agencies. A bit larger and heavier, size of a shoebox, mass ~10 kg. Contains cameras and various scientific instruments. No solar cells like the two rovers, but battery operated, able to provide power during 16 hours. Also able to hop, like the rovers.

This is an artist impression of the MASCOT, leaving its container in Hayabusa2.

During the descent, Hayabusa2 was able to follow the lander. The yellow line is the actual path, the blue line is the projection on Ryugu’s surface. The times are given as “hhmmss”. After it hits the surface, it bounced several times. During the last part (straight blue line),no pictures were taken. The location 02:14:04 is the final landing place. The separate location 00:55:09 +1 is taken one day later and proves that MASCOT has managed to hop. The shadow is from Hayabusa2

Here are two images taken by MASCOT itself. Left while descending to the surface and yes, that is its own shadow top right. Right after landing, again showing a very rough surface.

After the successful landing, MASCOT started to use its scientific instruments (spectrometer, magnetometer and radiometer) and sent the data back to Hayabusa2 within the limited timespan of 16 hours. Actually the batteries lasted one hour more, a bonus. It hopped two times.

Until now the mission has been very successful: two rovers and one lander have touched an asteroid for the first time in history!

What will be next? The main mission is to collect material from Ryugu and bring it back to Earth. How to do that? Here is a schematic view of Hayabusa2. Notice the .Sampler Horn at the bottom

This is the procedure: the Hayabusa2 will descend very slowly to the asteroid until the horn touches the surface. Then a small (5g) bullet will be fired inside the horn, hit the surface at high speed and surface particles will fly up and be collected at the top of the horn. Hopefully at least 0.1 gram, maximum 10 gram. This will be done at two different locations.

The third and last one is quite spectacular, an attempt to collect material below the surface. Here is another view of the bottom of the spacecraft. Next to the horn you see the Small Carry-on Impactor.

It is an explosive device, meant to create a crater in Ryugu, so that Hayabusa2 can collect the debris. Here is how it works . The explosive will deform the copper shield (2.5 kg) into a projectile, that will hit the surface at a speed of 2 km/s, creating a crater with a diameter of several meters

By the way,  this is where the idea may have come from…:-)

The explosion must of course not damage Hayabusa2 itself! The  scientists have found this spectacular solution:

  1. Hayabusa2 approaches the surface of Ryugu.
  2. It releases the bomb and also a camera.
  3. Then it moves up and sideward to hide itself behind the asteroid!
  4. The bomb explodes and creates a crater.
  5. The camera takes images and sends them to Hayabusa2.
  6. Hayabusa2 appears again and descends above the crater.
  7. The horn will collect debris of the explosion

Here is an artist impression, where Hayabusa2 is descending above the newly formed crater.

The first touchdown of the spacecraft itself was planned for end October, but it has been postponed until January 2019.

Why?

Because the surface of Ryugu is much rougher than expected!

The horn of Hayabusa2 extends about 1 m, therefore the touchdown area should not have rocks higher than 50 cm. The touchdown area must also have a diameter of at least 100 m because of navigational accuracy.

Such a location could not be found on Ryugu!. Below is the one finally chosen (red circle) free of rocks, but ONLY 20 m in diameter!

There is also some good news. The earlier launching of the rovers and the MASCOT showed that navigation (with laser range finders) could be done more accurately (within 10 m), at least until the altitude of 50 m above the surface.

In the next weeks, two rehearsals will be performed, going lower, to find out whether tis accuracy can be maintained until touchdown.

The first real touchdown is now planned for January next year. There is enough time because Hayabusa2 will stay at Ryugu until December 2019.

All this is happening at about 300 million km away from Earth. Amazing. Keep in mind that communication between Earth and the spacecraft takes about 15 minutes, one way!

The German Space Agency has published a very instructive YouTube video, illustrating what I have tried to explain in this blog. Not only about the MASCOT lander as the title suggests.  Worth viewing more than one time!

If more news becomes available I will write an update

 

The Marker Wadden

Would you like to go with me to the Marker Wadden, my youngest brother asked me during my recent visit to the Netherlands.  The Marker Wadden? I knew about the Wadden Islands and the Wadden Sea, but had never heard about the Marker Wadden.

He explained to me that it was a project of Natuurmonumenten, the Dutch Nature Society, to create a number of artificial islands in the Markermeer.

Ok, I knew about the Markermeer. Have a look at the left map, taken from the informative Zuiderzee Works entry in Wikipedia. After closing the Zuiderzee with the Afsluitdijk in 1932, it was renamed IJsselmeer, and gradually changed from a salt water lake into a fresh water one. Large parts of the lake were reclaimed to form polders. The original plan was to reclaim also the Markermeer, and a dike, the Houtribdijk, was already built between 1963 and 1975.

But the reclamation plans changed, and in 1986 it was decided that the Markermeer will remain a lake. When you look at the right picture, a Google Earth map of the same region, you will notice the different color of the water in the Markermeer. Because the lake is separated by a dike from the IJsselmeer, there is a lot of siltation, resulting in turbid water. This has a negative impact on the aquatic flora and fauna.

In 2012 Natuurmonumenten,  with other partners, presented an ambitious plan, to create  a couple of artificial islands in the Markermeer, using sand and silt from the bottom. The islands will not be used for human habitation, but will become a bird sanctuary.

The project has been accepted and is now in progress, with support of several sponsors. In the left picture you can see the location of these Marker Wadden relative to the Houtribdijk. The right images shows more details, the north-west island has a harbour and some infrastructure (footpaths and walkways), this island will be accessible to the public (but only if you have your own boat!). The other islands will be strictly nature reserves.

To show these Marker Wadden to the general public, Natuurmonumenten organised a temporary ferry service during the weekend of  8-9 September and my brother bought tickets, for of course I eagerly accepted his invitation…:-)

The ferry left from the Bataviahaven in Lelystad. We arrived early, so we could have a nice seat and a cup of coffee. Many interested people, often  armed with binoculars and cameras.

After about 45 minutes we arrived at the jetty of the Marker Wadden

There were two walking routes on the island, 2.5 km and 6 km. We took the shorter one. At the start it looked like a crowd, but it spread out quite fast.

Work is still going on, but this was a weekend, so no activity.

Here I am posing as a climber of the Marker Wadden mountains…:-)

There is a lookout tower, solidly built.

From the balcony at the top you have a good view of the surroundings.

It was an interesting walk, In many places the work was still in full swing.

A warning sign for dangerous quicksand.

Regarding plant life, the philosophy of Natuurmonumenten is to let nature take Its course.Slowly  plants will start growing, from seeds blown over by the wind from the surrounding polders. I have my doubts about the single patch of sunflowers I saw…:-). Could it be that somebody has bought  a packet of sunflower seed and sowed it here?

We walked over a nice walkway, sat down and had the sandwiches we had taken from home. In a few years time this will be a beautiful region.

It will also become a paradise for bird watchers. During our visit we did not see many birds, because it was  not the migratory season yet.

We spent a few hours on the island and then took the ferry back to Lelystad. A very nice outing.

 

Leiden 2018

Most of my life I have been living in Amsterdam, but I was born in Alphen aan den Rijn, a small town 15 km from Leiden. Of course I have been in Leiden many times in my youth, but I have never really explored the town.

Therefore, on the first Sunday in September, I  took the train to Leiden Central Station and visited the town. Leiden has a long history. It  received city rights in 1266 and flourished in the 16th and 17th century, because of the cloth industry. Here is a map of Leiden in 1690

And here is a Google Earth view from 2008. It is remarkable how the historic town center is still easily recognisable. The blue markers indicate some of the locations where I have taken pictures.

The 1690 map is full of interesting details, Click here for a large size image. Count the windmills on the city walls! And notice that numerous canals have nowadays been filled in to become roads.

These days only two windmills are left. The Valk mill will draw your attention when you walk from the station to the old town. The water in the foreground is one of the singels (moats) surrounding the 17th century town.

De Valk is a tower mill, built in 1743, replacing an older mill. In the past the miller was living in the mill with his family, nowadays it is an interesting museum. The mill is built so high to catch the wind. In the right picture you see the wheel to rotate the top of the mill in the direction of the wind. This is a cornmill and still operational

The lower floors show how in the past people were living here.

You have to climb many steep ladders to reach the top of the mill. The complicated machinery (wooden gears!) always fascinates me.

The second windmill on the ramparts is the mill de Put. Although there has been a mill here since 1619, several times rebuilt, it was destroyed in 1817. Only in 1983 the mill has been reconstructed and is now a museum. It is a so-called post mill, the whole mill structure can be rotated around a central axis.

The mill was under renovation when I visited Leiden. The bridge in the foreground is also a recent reconstruction of an old bridge. It is called the Rembrandt bridge, because not far from here Rembrandt, the famous Dutch painter, was born in 1606.

In a small park nearby there is information about him, with his statue, painting of course. All tourists want to have their picture taken here, and so did I…:-)

Both tourists and locals were enjoying the beautiful sunny weather. The cafe terraces, which in Leiden are often placed on floating pontoons, were crowded.

In the morning, the sky was incredibly blue. Left the monumental facade of the Stadstimmerwerf (town carpenter’s yard) built in 1612. Next to it the Doelenpoort (1645), in earlier days the entrance gate to the exercise grounds of the Schutterij , a typical Dutch institution in those days. Many houses had characteristic stepped gables..

Leiden has the oldest university of the Netherlands, founded in 1575. It is still one of the  important ones, the royal family has been studying here.

This is the Academiegebouw, the oldest building in Leiden, in 1516 built as the chapel of a Dominican monastery. SInce 1581 it has been used by the university, nowadays mainly for ceremonial functions.

The Pieterskerk is the oldest church of Leiden, building started in 1121 and lasted hundreds of years.  It is within walking distance from the Academiegebouw and  a cortege of professors walks twice yearly from the university to the church, for the dies natalis (anniversary) and  for the opening of the Academic Year. An old tradition, this year the 443th time! When I visited Leiden, they were very busy in the church with preparations for the ceremony the following day.

I would really have loved to watch the procession. Here is a video taken during the dies natalis ceremony of 2016. Fascinating.

The church had a 110 m tall tower,which collapsed in 1512 and was never rebuilt. Not so easy to take an overall picture of this church, also because houses have been built against the church walls.

The interior of the late-gothic building is very impressive. Of course it was originally a Roman-Catholic church, but after the Reformation and the infamous Beeldenstorm in 1566 it became a Protestant church in 1572.

Many famous people were buried here (Jan Steen, Boerhaave), but I had no time to find their tombs. Just a few more pictures. The magnificent Van Hagerbeer organ is from 1643.

The Hortus Botanicus (botanical garden) of the Leiden University is the oldest in the Netherlands and one of the oldest in the world. I had never before visited the Hortus, and spent quite some time there.

There are many greenhouses with tropical plants. Probably the most famous one is the Victoria amazonica, with leaves that supposedly can carry a  baby.

The park is  very attractive.  Left  a view of the singel, right the Japanese garden

Also in the garden is the Leiden Observatory. It is one of the oldest in the world, originally housed in the Academiegebouw. In 1860 it was moved to the Hortus and in 1974 to the science campus, outside the town center.

After my visit I had lunch in the Hortus cafe

Leiden has numerous “hofjes” and I visited three of them. A “hofje” is a courtyard with almshouses. Rich people in the 17th century founded such hofjes as a charity. The almshouses were meant for various groups, poor people, or spinsters, or foreigners without family, etc.

Nowadays they still have rules and regulations for the tenants. They are oases of tranquillity, many of them have free access , but you are expected to be quiet and not disturb the people living there.

Jean Pesijnhof (1683)

This hofje, near the Pieterskerk, was founded by the widow of Jean Pesijn. They came from France, had no children and the almshouses were meant for members of the Walloon Church. A beautiful, idyllic courtyard.

Eva van Hoogeveenhof (1652)

Eva came from a wealthy family and never married. As the inscription above the entrance gate says, she was a “virgo castissima et laudatissima” (Google for translation). In her will she had stated that the almshouses were meant for honest women, above 40 year old and unmarried..

Van der Speckhofje (1645)

Also know as St Pietershofje. A secluded one, you can easily miss the entrance gate.Founded by Pieter Gerritsz. Van der Speck. In his will he stated that four of the eight almshouses were meant for widows, the other four for elderly couples. Nowadays younger people are housed in this little gem.

The town hall of Leiden stood in the Breestraat as early as the Middle Ages. In 1596 it was given a new facade in Renaissance style to show the importance of the town. It still looks impressive, although it is “new”! In 1929 a devastating fire destroyed the town hall, leaving only a skeleton of the facade.  In 1932 it was rebuilt , the facade in the original style, the tower in a different location and the rest in modern style ( a design by Dudok was rejected, understandable, but still a pity!)

Some details of the facade

The Burcht of Leiden is a fortress built on an artificial hill, constructed in the 11th century, located where two tributaries of the Rhine come together.

Here is the south gate (1651). access is free, it is a pleasant park.

From the ramparts, you have a view of Leiden. Here two churched I had no time to visit, left the Hooglandse Kerk, a gothic church from the 15th century, right the Marekerk, built in classicist style and opened in 1649. The Hooglandse Kerk was of course built as a Catholic church and only after the Reformation transformed into a Protestant one. The Marekerk was designed as a Protestant church.

I could not resits the temptation to have Poffertjes, a traditional Dutch mini-pancake. Served with butter and sugar, not healthy, but so delicious.

With my interest in architecture, I could have spent many days in Leiden. The Lakenhal was built as a guild hall for cloth merchants and is now an important museum, but closed for renovation during my visit. The Hartebrugkerk is the first Catholic church in Leiden built after the Reformation.

The Koornbrug is from 1642. It was so named, because for many centuries corn was traded on this bridge

With its many singels and canals, Leiden looks a bit similar to Amsterdam. Here  is a collection of photos taken during my visit.

After a long day it was time to go back to Amsterdam. The central station is an attractive modern building from 1996.

Walking to the entrance of the station,  I came across a pavement decoration, which did not make much sense to me (left picture) . Until I walked past and watched it from the other side (right picture). A spectacular anamorphic work of art!

It was a very enjoyable day!