Entries Tagged 'Space' ↓

A few months ago I wrote about the launch of the Mars Reconnaissance Orbiter, which will map the surface of Mars with an amazing level of detail and send data to Earth at very high speeds, compared to the previous probes sent there.

Well, the MRO arrived last weekend, and the orbital insertion maneuver was successful. You can see its present location with the Solar System Simulator images. It is now in a highly elliptical orbit that takes 35 hours to be completed, but it will spend the next few months adjusting to a closer and more circular orbit, 300km above the surface.

And, to mark the occasion, you can now explore the red planet without leaving your seat: enter Google Mars. The whole planet seems to be covered (except maybe the poles; I couldn’t find the polar caps) with three choices of views: visible, infrared and an color-coded elevation map. The resolution is not very high, except for some areas in the infrared view (such as the surrondings of Olympus Mons), but the views are great.

I really hope that these images get updated with MRO data when it becomes available. And, maybe, in 2015 we’ll all be looking at Google Pluto…

Interesting developments… it looks like 2003 UB₃₁₃, about which I wrote here and here, is smaller than it was thought. It is so reflective that it looks larger than it is, and this means that it may not be larger than Pluto after all (update: it turns out that it is, indeed, 30% larger than Pluto). Not that this changes much about the discussion of whether it is a planet or not, and the same goes for Pluto.

And, speaking of Pluto, New Horizons is on its way there, and you now can see exactly where it is. It is the fastest spacecraft ever made: it crossed the Moon’s orbit barely nine hours after its launch. But it will still take ten years to get to Pluto, even after a gravity-assist maneuver around Jupiter. When it gets there, it will study closely Pluto and however many moons it has: it looks like two more, in addition to Charon, were recently found. If New Horizons is as effective at finding moons as the Voyagers where, people should start thinking about new names before it gets there… (then, again, Earth-based telescopes get better every day; in ten years we may well have found them all)

A few weeks ago I watched Tom Hanks’ IMAX documentary “Magnificent Desolation: Walking on the Moon 3D” at the Melbourne Museum theater. It is very good, even though it had to work around the fact that the original footage (as in, footage taken by astronauts) was, obviously, not made for IMAX and would look terrible if blown up to fill a 20-meter-tall screen. Some scenes were “reenactments”, using the whole screen and 3D effects, while in others they framed the original footage so that it was shown in a more reasonable size. It’s one of those movies that make you walk out of the room feeling “inspired”.

Now I already know what is the next one I want to see: “Roving Mars“, a Disney production about the two Mars rovers, Opportunity and Spirit, that have been moving around the planet for the last two years. It comes out in the US today, but there seems to be no release date for Australia yet. Oh, well. Let’s sit and wait.

On the subject of “beyond”, it looks like there is now a modified theory of gravity which incorporates quantum effects and that explains the Pioneer anomaly and does away with the need for dark matter to explain other phenomena. It still needs lots of work, though, so that it is able to explain other things already covered by the accepted theories. Exciting stuff, anyway.

While most people tend to focus on Mars when thinking of exploring planets in Earth’s neighbourhood, the European Space Agency is taking some time to move in the other direction by sending a probe towards Venus, our other neighbour.

Of all planets, Venus is the most similar to Earth in terms of size and gravity, but its enviroment is even more hostile to humans than that of Mars. It is dominated by a runaway greenhouse effect that keeps surface temperatures above 400°C and a pressure 90 times greater than that of Earth. Its atmosphere is composed mainly of carbon dioxide and is permanently clouded, hiding the surface from view (and, probably, keeping the temperature lower than it would otherwise be). One other unusual feature of the planet is the orientation of its axis, which is tilted so much that the planet rotates in the opposite direction as compared to all others (except Pluto, which is always an exception, and Uranus). Also, the rotation is so slow that one local year is equivalent to less than two local days.

ESA’s Venus Express was launched yesterday morning (Australia time) from Kazakhstan, and will reach Venus in 162 days, on 21 April 2006. The probe is expected to remain in operation for two Venusian days (that is, approximately 15 Earth months) and to make several measurements of atmosphere dynamics and temperature distribution, trying to infer clues about the characteristics of the surface.

The former Soviet Union was the pioneer in the exploration of Venus, with 16 Venera probes launched between 1961 and 1983. Venera 3 was the first man-made object to land (or, more accurately, crash) in another planet, and Venera 4 the first to send data from an alien atmosphere. In all, the Venera probes returned an impressive amount of data, including chemical analysis of soil samples, surface images and video, and even sound recordings. Unfortunately, due to the severly hostile enviroment, none of the probes lasted for more than a few hours on the surface.

Venus Express is expected to help us understand the workings of the Venusian climate and, hopefully, of the origins of its greenhouse effect, without which it would have an enviroment not very dissimilar from ours. Since we may be starting to deal with a (much smaller) greenhouse effect of our own, Venus may teach us many lessons in the future.

Launched on 12 August and scheduled to arrive to its destination on 10 March 2006, the Mars Reconnaissance Orbiter will bring something very important to Mars: high-bandwidth communications.

The MRO will spend its first six months in Mars slowly adjusting its orbital path, doing several aero-braking manoeuvres over more than 500 orbits until it settles on a path 300 km above the surface. From there, its high-resolution cameras will be able to photograph features that are less than one meter wide. And, when I say high resolution, I mean it: the main optical instrument, named HiRISE (High Resolution Imaging Science Experiment), is actually a 20-inch telescope coupled to a 800-megapixel digital camera. As an example, the photo on the left is the Earth’s Moon seen by that camera from a distance of 10 million kilometres.

This will, of course, generate huge amounts of data to be sent to Earth. Due to the large distances involved and the difficulty of sending high-powered equipment to space, exploration vehicles have always returned data to Earth somewhat slowly. One of the more recent missions, Europe’s Mars Express (which is used to relay part of the data generated by the NASA surface rovers Spirit and Opportunity), sends data at no more than 200 kilobits per second (and as little as 30 kilobits per second, depending on conditions). The previous rover mission, Pathfinder, sent data at 1 to 2 kilobits per second, and the even older Voyagers managed up to 7.2 kilobits per second (as they didn’t have to land, they had larger antennas and heavier transmitters).

Clearly this would be less than appropriate for a spacecraft that can generate the equivalent of a 1,000 megapixel image every three seconds (and that is not counting the other instruments on board, plus occasional data relayed from the surface rovers — current and future). For this reason, MRO was fitted with a telecommunications system that includes a very large antenna (3 meters across), a fast computer and a high-powered (100 watt) transmitter which will allow it to send data at up to 6 megabits per second. Considering that this data will be sent over more than 100 million kilometres, that’s very impressive.

Together with this, the craft has also a second transmitter that will be used to test communications with Earth over a different range of frequencies (32 Ghz – Ka Band – instead of the usual 8 – X Band); if the test is successful, the new band can be used in future missions to increase even more the data rate of transmissions. The reason the higher frequencies aren’t used already is that transmissions in that range are more “fragile”, and are especially sensitive to moisture in Earth’s atmosphere (that is, if it rains, you’re out of luck). Better equipment and higher power may be enough to overcome these problems, and that’s what will be tested.

During its full mission (which lasts until 2010), MRO is expected to send 34 terabits of data to Earth; that is more than the amount of data returned by all previous JPL missions put together. It is expected to increase our knowledge of the red planet by orders of magnitude, and open the way to future scientific missions already being developed.

Interesting developments in the outer solar system: it turns out that 2003 UB₃₁₃, the possible 10th planet (code-name “Xena”), has a moon. That body, which I discussed in a previous post, is larger than Pluto and orbits the Sun in such a way as to intersect Pluto’s orbit, which makes it the most similar body to other planets that was discovered so far.

The moon doesn’t have a name yet (it was discovered less than a month ago, on 10 September) and is officially known only as “S/2005 (2003 UB₃₁₃)”. The discoverers are calling it “Gabrielle”, though (understandably). Its discovery is very important because it will help astronomers to find out how massive “Xena” is by studying the way the moon orbits the main body.

Oddly enough, the discovery of a moon around it doesn’t mean that “Xena” has any more hope of being called a planet than it had before. Many other bodies in the solar system have moons around then, including several small asteroids in the belt between Mars and Jupiter.

This is one of the most interesting questions raised by the fleet of unmanned spacecrafts floating around (and outside) the Solar System. In short, the Pioneer probes are not where they should be, and nobody knows why.

The two Pioneers (10 and 11) were launched in late 1972 and early 1973 and are currently two of the most distant man-made objects in existence. Neither of them is active anymore; the last signal from Pioneer 11 arrived in 1995, and from Pioneer 10 in 2003. They are still moving away from us in more or less opposite directions: 10 is heading to Aldebaran, which it should reach in about 2 million years, and 11 will fly by the constellation of Aquila in 4 million years.

Being this far away from us and having travelled for such a long time, they are in an excellent position to show us unexpected news about the way the universe works, and they may have done just that. Their actual position over the last few years was consistently “wrong” when compared to their expected position; the error indicated that they were being subjected to a small force towards the Sun that exceeds what should be expected from gravity and other known effects.

Nobody knows what that force is, of course. It could be something as simple as a gas leak, but it would be definitely strange that this would cause exactly the same amount of force applied in the same direction in both probes (then, again, they are identical; if it’s a design problem or side-effect, it’s not so far fetched as it sounds). It could also be an observational error; old data is being revisited to try to rule this out.

We do have different probes that are as far away as the Pioneers: Voyagers 1 and 2 are still operating and have already left the outer-most planets behind; Voyager 1 is, in fact, farther away from the Sun than any other probe (Pioneer 10 trails it by almost 1 billion kilometres, and Voyager 2 by 3 billion). However, the Voyagers are too different from the Pioneers: their stabilization system is different, and it causes thrusters to fire quite often to keep them pointed in the right direction; these thrusters interfere with the trajectory of the ships and, thus, with the very small effect of this unknown force. Still, they seem to be affected in the same way, although data is not quite conclusive. The probes Galileo and Ulysses, which are stabilised in the same way as the Pioneers, never ventured so far away from the Sun that the effect on them could be conclusively measured.

It is expected that New Horizons, the new mission to Pluto, planned to be launched early next year and to reach Pluto in 2015, could bring some light to this issue; as the Pioneers, it is spin-stabilised and should be affected by the same forces. Whatever the reason for the anomaly turns out to be, and even if it is indeed something quite prosaic, we will certainly learn something new: either about some aspect of space flight that was previously overlooked, or about some new facet of the inner workings of the universe.

Funny how things come and go. Last year, when Sedna was discovered, it was announced as a possible 10^th planet; however, there was also talk of not only not considering Sedna as a planet but also demoting Pluto to a more general “Kuiper belt object”, leaving us with 8 planets again.

Then, earlier this year, an as-yet-unnamed object (2003 UB₃₁₃, unofficially referred to as Xena or Lila) was discovered that is larger than Pluto, and considerably farther away (Sedna is smaller than Pluto and, therefore, more easily brushed aside). This is one of possibly thousands of similar objects orbiting the Sun from very, very far away. Are those objects planets?

It turns out that it is very difficult to come up with a scientific definition of planet that will include the current set of nine and nothing else. It would be easy if Pluto were demoted; then you would be able to define based on size (it’s very unlikely, although not impossible, that there’s any undiscovered object larger than Mercury orbiting the sun) or even on distance from the Sun (which is somewhat arbitrary, though), or you could pick the definition currently chosen by many scientists: a large body that dominates a particular orbit. Pluto does not fit (Neptune would be the dominant body in that orbit), and neither do the inner Solar System asteroids or any of the Kuiper Belt objects (no single body dominates those orbits). However, any definition that tries to include Pluto will, certainly, include many other bodies.

The current set of nine planets is a historical accident: when Pluto was discovered, it was thought to be an one-of-a-kind object, which would make it an odd planet but not much of a problem. The subsequent discovery of the Kuiper belt opened a can of worms, of which at least two jumped out so far: Sedna and “Lila”. Nowadays, the working definition of “planet” is “whatever the IAU says is a planet”, and the IAU is working (without much success) to come up with a ruling on the new bodies and, presumably, any new ones that pop up.

Personally, I’d like to see “Lila” accepted as a planet, but I recognize that this would bring a different problem: we could end up with hundreds of planets over the next few decades, and that would trivialize the word “planet”. Nine is ok, ten is fine, eleven is all right… 137 may be a little too much. I think the easiest solution is to keep the name for the current nine planets for historical reasons (or add “Lila” as the 10^th planet to recognize its discoverers), retire the word “planet” as a scientifically significant word (therefore freezing the set of planets in the actual configuration) and adopt an official naming convention based on the characteristics of the objects being named. This would probably make everyone happy without being too disruptive.

There seems to be a renewed interest in space exploration, especially in big projects, lately. Or is that just my impression?

We had NASA saying that we’ll have people on the moon again by 2018, which seems to fit with what Pres. Bush said a few months ago. Very interesting project, and I hope it does happen (still, 13 years is a long time to sustain funding…).

Then the August edition of IEEE Spectrum has a cover story on space elevators, making the point that now would be a good time to start building one. A space elevator could reduce the cost of putting materials in orbit from US$20,000 a kilogram to around $200. According to a presentation I found at spaceelevator.com, the budget for a single elevator is around $10 billion US dollars, already including legal costs (I can imagine the cost of liability insurance…). Meanwhile, an American private company (Liftport Group) got FAA clearance to perform tests related to building an elevator; their homepage even counts down to their expected lift-off date (12 April 2018; what is it with 2018?).

Interestingly, the NASA plans for space exploration in the late 1960s included permanent moon bases by the early 1980s, and manned missions to Mars by 1985. Even the Shuttles should have been in space by 1973, if I’m not mistaken (the first launch was in 1981). We all know what happened, of course. Even the Apollo program only really succeeded because of the Russian competition, which prompted Kennedy’s challenge (put a man on the moon and bring him back by 1969); we don’t have anything like that now. Let’s wait and see.