The Fiery End of Jules Verne

•September 30, 2008 • Leave a Comment

Jules Verne successfully completed its six-month mission when it re-entered our atmosphere and burned up over the South Pacific.

Jules Verne reentry.

Jules Verne reentry.

First images received from the DC-8 aircraft which observed the re-entry of Jules Verne ATV over the Pacific Ocean. Credits: ESA.

Its final de-orbit burn slowed its velocity to 70 m/s and it broke up at an altitude of 75 km with the remaining fragments falling into the Pacific some 12 minutes later.

“Credit has to go to everyone involved in such a flawless mission.” said John Ellwood, ESA’s ATV Project Manager and he is looking forward to the launch of the next ATV, which is currently under production at EADS Astrium in Bremen, Germany.

Posted in Satellites & Spacecrafts
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Goodbye, Jules Verne

•September 29, 2008 • 1 Comment

Remember Jules Verne? The ESA Automated Transfer Vehicle (ATV) that visited the International Space Station (ISS) last April?

After a flawless six months mission, Jules Verne undocked from ISS early this month and after 23 days flight above our sky, it is now heading for a controlled destructive re-entry into Earth’s atmosphere later today.

Jules Verne

Backdropped by the Earth, ESA’s Jules Verne ATV continues its relative separation from the International Space Station. The ATV undocked from ISS on September 5 and scheduled re-enter Earth’s atmosphere on September 29. Credit: NASA

Jules Verne has surpasses all expectations: it successfully performed a fully-automated docking with the ISS; delivered the necessary supplies to the space station; re-boosted the station to higher orbit due to atmospheric drag; performing an debris avoidance manoeuvre for ISS; removing waste and garbage from the space station; provided a new hygiene station and even sleeping quarters. The ATV has truly demonstrated all its key capabilities, and more.

The ATV will enter the atmosphere over a completely inhabited area of the South Pacific to be viewable from the ISS. This huge “fireball” will also be observed by two specially-equipped observation aircraft to be deployed at monitoring locations in the region.

It’s a sad ending for such a wonderful spacecraft, and it seems like a waste just to burn it up like that… but this was what Jules Verne designed to be – a disposable, single-use re-supply ship for the space station.

As it dives into our atmosphere for a fiery end later today, we can only look up and say: “Goodbye Jules Verne…” (although I don’t think we can see it)

Posted in Satellites & Spacecrafts
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Carnival of Space #72

•September 28, 2008 • Leave a Comment

This week Carnival is held at Twisted Physics.  As usual, a lot of articles to keep you busy reading!

Posted in Carnival of Space

China’s Maiden Spacewalk a Success

•September 28, 2008 • Leave a Comment

China’s first-ever spacewalk is a success, so China now is the third country after the former Soviet Union and the United States to accomplish a spacewalk.

Chinese taikonaut Zhai Zhigang wearing the homemade Feitian spacesuit, pulled himself out of the orbital module of Shenzhou-7 at around 4:43 pm local time. He waved to the camera mounted on the service module and said: “I feel well. I am here greeting the Chinese people and people of the whole world”.

Shenzhou-7 EVA

This video grab is taken on Sept. 27, 2008 in Beijing, China, shows Chinese taikonaut Zhai Zhigang outside the orbital module. Credit: Xinhua Photo

Minutes after Zhai was outside the capsule, teammate Liu Boming also emerged briefly and handed Zhai a Chinese national flag that Zhai waved in the outer space against the backdrop of the blue planet Earth. The third crew member, Jing Haipeng, monitored the ship from inside the re-entry module.

Outside the capsule, Zhai retrieved a test sample of solid lubricant placed outside the orbital module and handed it over to Liu. Then the “real” spacewalking started. Tethered to the spacecraft with two safety wires and a long electric cord providing oxygen and communications, Zhai moved slowly along a set of handrails around the orbital module.

After staying outside in space for about 20 minutes, the taikonaut returned to the orbital module in a foot-in-first position, marking a complete success of China’s first space walk.

Source: Xinhua News

Shenzhou-7 Spacewalk

Posted in Human Space Explorations
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China’s 3rd Manned Space Mission and its Maiden Spacewalk

•September 27, 2008 • 1 Comment

Shenzhou-7 launching

The Long-March II-F carrier rocket carrying the Shenzhou-7 spaceship blasts off from the launch pad at the Jiuquan Satellite Launch Center on 21:10 pm, Sept. 25, 2008. Credit: Xinhua/Li Gang.

China has successfully launched its third manned spacecraft Shenzhou-7 last Thursday from Jiuquan Satellite Launch Center in Gansu province of northwestern China. There are three taikonauts (Chinese astronauts) onboard, namely Zhai Zhigang, Liu Boming and Jing Haipeng, all aged 42. 

Shenzhou-7 taikonauts  

The Jiuquan Satellite Launch Center held a ceremony Thursday afternoon for the three taikonauts due to board the Shenzhou-7 spacecraft before the start of the mission. Credit: Xinhua Photo

The spacecraft, which consists of the orbital module, re-entry module and propelling module, is designed for a voyage of up to five days. But the Shenzhou-7 mission will only last about three days, flying in a circular orbit 343 kilometres above the Earth, orbiting every 90 minutes.

Shenzhou-7 is China third manned spacecraft, after Shenzhou-5 and Shenzhou-6. This mission is different from the previous ones in the sense that it will attempt the country’s first-ever extravehicular activity (EVA) or spacewalk.

Although there are three taikonauts onboard, only one taikonaut will perform the spacewalk and it has been confirmed that it will be perform by the mission leader Zhai Zhigang. Zhai will be assisted by a second taikonaut, Liu Boming, in the orbital module. The third astronaut, Jing Haipeng, will remain in the re-entry module during the whole process of the spacewalk to keep an eye on the vessel operation. The spacewalk, expected to last about 30 minutes, is scheduled to take place at 4:30 pm today.

There are two different spacesuits for the taikonauts. One is a home-made suit called Feitian, which literally means flying the sky, which cost about 4.4 million USD, and takes up to 15 hours for taikonaut to assemble and put on. The other one is a Russia-imported Orlan suit.

If Shenzhou-7 mission is successful, China will become the third country after the former Soviet Union and the United States to accomplish a spacewalk, a crucial capacity if China is to have its own permanent space station.

Shenzhou-7 scheduled to land on the Inner Mongolia steppe on Sunday after the mission is completed.

Animation of Shenzhou-7 Spacecraft

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Saturn’s Rings

•September 24, 2008 • Leave a Comment

Who can ever forget their first view of Saturn through a telescope? Even with a small telescope, its magnificent rings never disappoint anyone. And some even can’t believe that it’s real… they are wondering if I stick a picture of Saturn in front of my telescope…

Ah, the rings… the most dramatic features in the Solar System… but have you ever wondered where did they come from? Are they there since the beginning of the Solar System, or they are formed later in the history?

NASA/JPL/Space Science Institute

Actually, no one knows for sure. One of the possibilities is that in Saturn’s early history, an ice moon or comet came too close and was torn apart into pieces by Saturn’s gravity. Or it may be two objects collided, shattered and their pieces distributed around the planet and became the rings. It is also possible that the rings form from the leftover materials that never get to become part of the planet or moon.

Some of the fainter rings came from dusts and particles that gets knocked off from moons when they are hit by micro-meteoroids or from geysers spewing out from moons.

So we think we know where the rings came from.

But how long have they been there?

It seems not possible that the rings are as old as Saturn itself, which is about 4.5 billion years old. This is because the rings are too bright – if the rings are as old as the Solar System, then we would expect that dirt and dust created by meteoroid impacts covered up the rings’ particles. Over time, the rings will be darkened by meteoric dust. So if the rings are “clean and shiny”, it may imply that they are young; it was calculated from Voyager measurements that the rings are only about 100 million years old.

100 million years is only a very brief period in our whole Solar System history of 4.5 billion years. This implies that we are lucky – we happen to be around at the right time to see the rings.

There is a basic statement in astronomy that we don’t live in a special place or in a special time. And it happens that we are around at this special time to see the rings make astronomers uncomfortable.

NASA/JPL/Space Science Institute

Recently a finding may make astronomers feel better. Both Cassini spacecraft‘s UVIS (Ultraviolet Imaging Spectrograph) instrument and theoretical calculations by its Principal Investigator Dr. Larry Esposito and his team can allow the rings of Saturn to be billions of years old. This means we humans are not just lucky to see rings around Saturn.

It was found that Saturn’s rings may be more massive than previously thought. The ring particles, instead of countless individual chunks of ice, tend to aggregate into clumps, which leads to an increase of mass by a factor of 3 or more. The new calculations show that if the rings are more massive, they appear less polluted, and thus could be proportionately older. Recycling of ring material can also extends their lifetime and reduces the expected darkening.

This model may not be perfect; but at least it can help to explain something.

Posted in Saturn

Autumnal Equinox

•September 22, 2008 • 2 Comments

To me, today – the Autumnal Equinox – is another “milestone day” in a year. This is the time when I sit back and think what have I accomplished or going to accomplish this year, and how much time I’m left with.

Equinox happens once every 6 months – Vernal Equinox in March and Autumnal Equinox in September. Midway between the two equinoxes we have the solstices.

Technically equinox is the time when the Sun crosses the celestial equator. For autumnal equinox, the Sun moves from north to south.

If you have ever paid attention to the direction of the Sun each morning on your way to work, you will observed that the rising Sun is constantly changing its direction everyday, moving sometimes from northeast to the southeast daily, sometimes the other way round. This is especially obvious if there is a building or tree as a reference point: the Sun doesn’t rise the same direction everyday.

The reason is simple: our Earth is tilted. This is exactly the same reason as why we have seasons.

Although we usually said that the Sun rises in the east and set in the west, in reality the Sun only rises exactly due east and set exactly due west only 2 times in a year, that is during the equinoxes. So today, the Sun rises exactly east and will set exactly west.

Season on Earth

Refer to the diagram above, which is a typical diagram when we learn about seasons in school, due to the axis tilt of our planet with respect to its orbit around the Sun, sometimes our Earth’s northern axis is tilted to the Sun and sometimes the southern axis is tilted to the Sun.

Another way of expressing is there will be time when our Sun is above or north of the equator and time when it is below or south of the equator. Only during the equinoxes, the Sun is exactly on the equator.

So, the Sun rises northeast from March to September, and then on today, the Sun will pass by the equator and heads south. After that from September to March next year, our Sun will rise southeast and set southwest. Then on the Vernal or Spring Equinox in March, the Sun once again passes by the equator and heads north and the cycle repeats itself.

Astronomy Picture of the Day has a nice photo showing the different position of the Sun for the northern hemisphere. Just bear in mind that this photo does not reflect our situation at the equator. At the equator, the “middle band” Sun should be directly overhead (at the zenith), while the solstice Suns (“top band” and “bottom band” Sun) are the same distance above the horizon.

Posted in General Astro Talk
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