{"id":6696,"date":"2014-11-10T00:43:13","date_gmt":"2014-11-09T16:43:13","guid":{"rendered":"http:\/\/stuif.com\/blog\/?p=6696"},"modified":"2014-11-14T13:20:51","modified_gmt":"2014-11-14T05:20:51","slug":"here-is-rosetta-again","status":"publish","type":"post","link":"https:\/\/stuif.com\/blog\/?p=6696","title":{"rendered":"Here is Rosetta again! (updated)<\/font>"},"content":{"rendered":"

In two earlier posts I have reported about the exciting space adventure of Rosetta, a spacecraft\u00a0launched in 2004 with as destination a comet, the\u00a0\u00a067P\/Tsjoerjoemov-Gerasimenko. The first post, Wake\u00a0up,\u00a0Rosetta!<\/a>, described how, after a hibernation of more than two and a half years, Rosetta woke up in January 2014, according to plan.<\/p>\n

The second post, Rosetta meets 67P<\/a>, published last August, reports\u00a0how Rosetta successfully goes into orbit round the comet. It turns out that the comet has a strange shape, like a rubber bathtub duck. \u00a0Here is a picture, taken on 19 September at\u00a0\u00a028.6 km from the center of the comet. The head points to the right. If you look carefully you will see a kind of smoke coming from the “neck” of the comet. That is the coma, part of the\u00a0comet material is evaporating\u00a0because it is approaching the sun. Later, closer to the sun, 67P will develop the characteristic comet “tail”. The comet is rotating with a period of 12 hours and 36 minutes.<\/p>\n

\"67P\"<\/a><\/p>\n

The last few months the scientific instruments on board Rosetta have already been busy. For example analysing the composition of the “coma” smoke. With interesting results, finding not only water and carbon dioxide, but also methanol, ammonia and hydrogen sulphide. Here is an interesting blog about The “perfume” of 67P<\/a>. \u00a0Quote: \u00a0If you could smell the comet, you would probably wish that you hadn\u2019t<\/span><\/p>\n

But the ultimate goal of the expedition is to land a module on the comet itself! This module has been called Philae and you can see it here still attached to Rosetta.<\/p>\n

\"Rosetta<\/a><\/p>\n

The last few months, \u00a0the scientists have been working hard to find a suitable landing site\u00a0for Philae. That has not been a simple job, because of the complicated structure of the comet. The landing site\u00a0should be relatively flat and smooth. Several options have been studied, finally the decision was made to choose location J, on the head of the duck in the picture below.<\/p>\n

\"Landing<\/a><\/p>\n

The landing site has now been renamed Agilkia. Why? Google and find out yourself \ud83d\ude42 Hint: there is a relation with Rosetta and Philae.<\/p>\n

The critical landing operation will take place on Wednesday November 12. At 8:35\u00a0GMT Philae will be deployed from Rosetta and start its slow fall to the comet. \u00a0It has no thrusters that can change its course, so ultimate precision is required in the timing of the separation. Keep also in mind that the distance between earth and the comet is at the moment about 500 million km, so signals take time to reach Rosetta. To be exact: 28 minutes and 20 seconds one way!\u00a0So it will be 9:03 GMT before we know if the separation has been successful.<\/p>\n

Falling to the comet?<\/span> Yes, because the gravitational attraction of the comet is very small, but it exists. The falling proces willl take about 7 hours! And the speed at landing will be “only” ~ 1m\/s. For comparison, that is the speed an object would get here on earth, when it falls\u00a05 cm!<\/p>\n

As soon as Philae touches the surface of the comet, two harpoons will be fired down to anchor the module. Otherwise it might\u00a0bounce back into space! Here is an artist impression of a successful landing.<\/p>\n

\"Philae<\/a><\/p>\n

The two red lines under Philae are the harpoons. The construction of the three supporting “legs” allows landing on moderate slopes. If the slope\u00a0is steeper than 30 degrees, the Philae might topple over, resulting in failure. The whole procedure is considered a risky one, success estimates of 75% “only” have been mentioned..<\/p>\n

So let us keep our fingers crossed Wednesday! Malaysian time is GMT + 8 hrs, Dutch time is GMT + 1 hr. Here is the ESA control room. How many nails will be bitten on that day, waiting seven hours, while you can do nothing…:-)?<\/p>\n

\"ESOC\"<\/a><\/p>\n

On Wednesday there will be a live broadcast of the landing procedure<\/a><\/p>\n

UPDATE 12 NOVEMBER<\/span><\/p>\n

5am GMT<\/span><\/p>\n

The Live broadcast has started already. It is still early in Darmstadt, people are arriving in the ESOC control room, where it is obviously quite cold…:-) Many sniffy people.<\/p>\n

Here is a diagram of what will happen today. As I explained in my post, after separation Philae will “fall” to the comet. No course correction possible after separation, so utmost precision is needed<\/p>\n

.\"Rosetta_s_trajectory_12_November_node_full_image_2\"<\/a><\/p>\n

The last few days pictures have been taken by Rosetta with amazing details. Click here<\/a> for a collection. Here is \u00a0a spectacular one.<\/p>\n

\"67P_detail\"<\/a><\/p>\n

7:30 GMT<\/span><\/p>\n

Just watched an interview with\u00a0Gerhard Schwehm, mission manager of the Rosetta project. Now retired. I did not realise that the project started in 1985, almost 30(!) years ago. Less than one hour now until separation.<\/p>\n

8:05 GMT\u00a0<\/span><\/p>\n

I have been naive..:-) Thinking that at this moment the command should be sent to Rosetta to deploy Philae (because it takes 28 minutes for the signal to reach Rosetta). But of course they will not do it that way..:-) \u00a0Rosetta has been programmed to deploy Philae at 8:35am ! \u00a0Around 9am GMT the ESOC will know if that separation has been successful.<\/p>\n

8:35am \u00a0GMT<\/span><\/p>\n

At this moment, 511 million km away, the Philae is starting its fall to the comet 67P. In spite of a problem that has been found in the \u00a0lander. As explained in my post, the Philae could bounce back after touching the surface of the comet. Therefore two harpoons are fired at touchdown to anchor it. Also, on top of the Philae, an amount of gas should be released, giving\u00a0the Philae an extra push to the surface. It seems that this “thruster” doesn’t work properly.So everything will now depend on the harpoons.<\/p>\n

9:05am GMT<\/span><\/p>\n

Separation is succesfull!!<\/p>\n

Waiting. Tense<\/p>\n

\"Waiting\"<\/a><\/p>\n

Relief. Hugging<\/p>\n

\"We<\/a><\/p>\n

From now on, the Philae is on its own. In two hours time hopefully contact will be reestablished between Rosetta and Philae<\/p>\n

11:10am GMT<\/span><\/p>\n

Contact established between Philae and Rosetta! Great! This is a bigger step than the deployment. Philae is too weak to communicate directly with Earth, it has to do that via Rosetta. And it did! So now we can follow its descent to the comet, and it may even be able to send pictures.<\/p>\n

Tension and relief again..:-)<\/p>\n

\"Waiting<\/a><\/p>\n

\"We<\/a><\/p>\n

2:20pm GMT<\/span><\/p>\n

The first image taken by Philae\u00a0of\u00a0Rosetta, just a short time after deployment. Unprocessed, so not high quality, but convincing proof that\u00a0Philae is on its way to 67P<\/p>\n

\"Rosetta<\/a><\/p>\n

2:40pm GMT<\/span><\/p>\n

Telemetry data from Philae show that it is following the calculated trajectory accurately. The landing will be the most critical part. Everybody at Esoc keeps his\/her fingers crossed.<\/p>\n

Here is an image taken by\u00a0Rosetta’s\u00a0Osiris camera of the descending Philae lander. Amazing. The landing arms are out.<\/p>\n

\"filae\"<\/a><\/p>\n

3:30pm GMT<\/span><\/p>\n

Waiting now for news about the landing. Personally I do no like the optimistic way of talking about success. There is a reasonable chance of failure, and then the disappointment will be huge.<\/p>\n

4:05pm GMT<\/span><\/p>\n

Success? Or not? It seems Philae has landed. Congratulations<\/p>\n\n\t\t