Entries Tagged 'Space' ↓

Dates

On the 12th of April, 1981, I was exactly nine and a half years old (half years are important when you’re that young). That was the date of the launch of the first Space Shuttle mission, STS-1, with the Shuttle Columbia spending the next two days in orbit with a small crew of only two astronauts (it was effectively a test flight). I was fairly young, but I do remember watching the news about the launch — it was a big deal at the time. I particularly remember that, differently from later flights, the external fuel tank was white, and not orange — orange is the “natural” colour of the protective foam around the tank, and painting it white added a significant amount of weight to the tank, so they stopped doing it at some point.

On the 28th of January, 1986, I was a bit over 14 years old. That afternoon I was at a friend’s place, his mother had the radio on and I heard something about a rocket exploding after launch in the US, but didn’t pay much attention to it; I didn’t know there was a Shuttle launch on that day, and assumed it had been an unmanned rocket carrying a satellite, or something similar. It wasn’t until I watched the news on TV at night that I knew what had happened to Space Shuttle Challenger, taking off for what was supposed to be mission STS-51-L. I remember being sad on that day and obsessively following the news for weeks after, and I was very happy when Discovery flew the first mission after the accident, in September 1988.

On the 1st of February, 2003, I was already an adult, and I was spending a quiet Saturday at home until I happened to look at the news online (I think it was on cnn.com) and read about what had happened to Space Shuttle Columbia, returning to Earth after mission STS-107. I very distinctly remember that my first thought was “not again!” — despite the 17 years that had passed since the previous accident. After that, I turned the TV on and just kept watching for however long they were talking about it. It was another sad day.

On the 21st of July, 2011, I will be nearly 40 years old. It will be 42 years and one day since the first Moon landing, and more than 30 years since that first Columbia flight. That is the scheduled date for the landing of Space Shuttle Atlantis, completing mission STS-135 — the final Space Shuttle mission, ever. It’s going to be, again, a sad day. I planned on writing more about it, but I don’t think I can do better than what astronomer Neil deGrasse Tyson (whom I had the opportunity to meet twice, and who is a great person to talk to) said on Twitter: “Many lament the shuttle era’s end. But that’s misplaced sentiment. Lament instead the absence of an era to replace it.”

He’s talking, of course, about the lack of a manned space program on the part of NASA for the immediate future (and, with the difficulties it’s been having to get its budget approved, perhaps the not-so-immediate future as well).

Still, NASA goes on, as does space exploration. Just this week, on July 16th, the spacecraft Dawn will go on orbit around asteroid Vesta — it’s the first probe ever to orbit an asteroid, and in the next few years it will become the first probe ever to orbit two different bodies, when it leaves Vesta to go after dwarf planet Ceres. New Horizons is still on the way to Pluto, which it will reach in July 2015. And many other missions are still flying around the solar system – and, with the two Voyagers, even outside it.

Here’s hoping for continued progress, and hoping that in the future we’ll be able to celebrate the Shuttles as a stepping stone, and not as the end of the road.

Pluto

The whole Pluto story has been all over the blogosphere and the regular media, so I didn’t talk about it much. In the end, I liked that the IAU reached a decision (disputed as it may be), even though I actually preferred the option that was announced the week before (12 planets, not 8).

The Australian “Cosmos” magazine has a good editorial online about why Pluto had to go; and, to be honest, I do hope this subject dies quickly and that people get it over with.

In other news, astronomy-related posts will now be found here; this blog returns to its regular programming.

Still about Pluto…

One other proposal that has surfaced for the definition of a planet is to accept anything that has an intrinsic magnitude (brightness) that is equal than or larger than Pluto’s. This would keep Pluto as a planet, and would also include 2003UB313, a.k.a. Xena, which would then (I suspect) be named in accordance with the naming rules for planets (names of Greek gods). Nothing else would make the cut, though — Sedna, Ceres etc. would not be considered planets.

The IAU conference happens over the next two weeks, and a blog with information on everything that happens (not only about Pluto, of course) is at http://astronomy2006.blogspot.com/.

Pluto still a planet, probably

Pluto and Charon - photo NASANPR reports that a IAU panel has unanimously recommended that Pluto (in the photo with its larger moon, Charon) keep its status as a planet, and it is possible that we may end up with several objects being recognised as new “dwarf planets”.

I mentioned a while ago that the IAU was going to decide on an unambiguous definition for the word “planet”, and that it was likely that this would change the number of planets in our solar system. The decision has not yet been reached; this should happen later this month. However, several members of the aforementioned panel suggest that Pluto will join a new group called “dwarf planets” (we already have “terrestrial planets” and “giant gas planets”), which might include any body that orbits the Sun and that is large enough that its own gravity makes it spherical (or nearly so); this would include anything larger than some 700km across.

This definition would include not only Pluto and Xena (a.k.a. 2006UB313), but also other smaller bodies such as Ceres (an asteroid between Mars and Jupiter). This would take the number of known planets to something like 13 or 14, but it is unsure whether this will be approved.

The IAU general assembly opens tomorrow, 12 August, in Prague.

Discovery is back

Discovery landsSpace shuttle Discovery landed safely last night (23:14 Melbourne time, 9:14 in the morning in Florida) at the Kennedy Space Center, ending mission STS-121. The mission achieved all its stated objectives, and the shuttle came back in perfect form, despite worries about a leak in a power unit (and the earlier worry about white markings on the heat shields).

It is expected that this will revitalise the shuttle program, with more lauches happening in the next few months. The next planned mission is STS-115, which will again deliver components to the Internacional Space Station. It will be the 19th shuttle flight to dock to the ISS, and it has no launch date set at this moment.

Why are the mission numbers in the wrong order? STS-121 has just landed; the last mission before that was STS-114, and the next is STS-115. Well, mission numbers are assigned when the mission is planned, years in advance. Intervening events can, and often do, change the order in which they are actually executed. A full list of missions, ordered chronologically, can be seen in NASA’s Mission Archive (note that, within each year, missions are ordered from last to first).

View from a booster

There’s a great video available in the website of the current shuttle mission (STS-121): it is the view of the launch from the camera mounted on the side of one of the boosters, looking towards the shuttle’s wing.

The video shows the launch, climb and separation, and keeps on following the booster falling back to Earth until it gently lands on the ocean and stays there, bobbing up and down, waiting to be rescued.

To view it (Windows Media only), go to the STS-121 main page and click on “Right Forward Solid Rocket Booster Video” on the right column, underneath “Related multimedia”. Or, if it’s not there anymore, try clicking here.

Shuttle status

The shuttle has reached orbit with no problems, as I reported yesterday; now, external examinations of the heat shields (using a remotely operated camera) show that everything seems to be ok with the ship, and that it should have no problems during landing.

In one of the few “comic relief” moments of the last weeks at NASA, officials reported that white markings found on the wings of the shuttle seem to be bird droppings, which were already there before the launch and are expected to burn on re-entry. It is entirely possible that bird droppings made it into orbit in previous flights as well, but they wouldn’t be noticed; the shuttle usually sits on the pad for quite a while before launch, and it makes a very large target for birds. The only difference is that people are paying much more attention to the shuttle these days…

Discovery launches

Discovery launch. Image credit: NASASTS-121 was launched today (04 July, Eastern US time) with no apparent problems, despite a crack in the insulation foam having been found days earlier. Discovery carries seven astronauts and will deliver supplies to the International Space Station; it will also test several newly-developed safety procedures.

This was the first shuttle launch in over a year, and a lot was (and still is) riding on it. A serious problem, if found, will almost certainly end the shuttle program with no new vehicle to replace it, which would severely affect the (already delayed) cronogram for finishing the ISS. Should a problem be found in the insulation while the shuttle is attached to the ISS, the plans call for the astronauts to be rescued with other vehicles (possibly the remaining shuttle, Atlantis) and for Discovery to be landed by remote control.

You can track the shuttle’s location in real time here. It will probably be interesting to look at this tracking during the ISS docking maneuvers.

Saturn and moons

Saturn has always been the most spectacular planet in the solar system, and it looks like every time you look you find a new satellite orbiting it; I think the total number is up to 47 already. Actually, it’s hard to give a precise number, and the problem is similar to that of deciding whether Pluto is a planet or not: technically, all of the small chunks of ice and rock that orbit Saturn, both independently and as part of its rings, are satellites, and there’s not a clear distinction between “small moon” and “large rock”.

In any case, the Cassini Imaging Lab has released a series of beautiful animations depicting the movement of Saturn and some of its moons. Definitely worth taking a look. The third one in particular, “Staying with Epimetheus”, shows quite clearly the amazing range of sizes the Saturnian moons come in.

And, admit it: you had no idea Saturn had a moon called Epimetheus, did you?

(on an unrelated note, Pluto’s new moons very officially named this week: they’re Nix and Hydra, joining the already known Charon; and the IAU should rule in September on what’s the official definition of a planet, so we may end this year with anything between 8 and 10 planets in our solar system)

The sky tonight

If you are in a location from which you have a reasonably dark sky and a good view to the west, go outside today just after sunset and look up. Saturn and Mars will be very close together somewhat low in the northwest sky, and this should be visible with your naked eyes from almost anywhere. The image you see here (generated with Stellarium) shows their relative positions as they will be around 18:30 tonight, in Melbourne; the view will be similar from other locations at similar local times. From Melbourne, Mars will set at 20:25 and Saturn right after at 20:41.

Also, if you go out a little earlier, Mercury will be making a very good appearance, much closer to the horizon; it will set at 18:41, so you will have to look for it against a sky that will still be a little bright.

The cluster of stars you see behind Mars in the image is the Beehive cluster (NGC 2632), but it will offer a much better view with binoculars than with your naked eyes.

If you can’t go out tonight, don’t despair: the two outer planets will be even closer at the same time tomorrow, but Mars will have almost finished clearing the Beehive by then. If you want to catch Mars on top of the cluster, this is the day.

Choosing binoculars – part 2

In part 1, I covered three important variables to watch for when choosing a binocular: magnification, aperture and the size of the exit pupil. Now, I’ll go through a few more.

Coatings

Gathering light is important, but not losing it after it’s gathered is just as important. Every time light crosses from air into glass or vice-versa, not all light actually gets through: some of it is reflected or scattered away. The loss of light can be of up to 5% on each transition, and a binocular may have as many as 16 air-to-glass or glass-to-air transitions inside it. This could cause as much as 55% of the light to be lost before it reaches your eyes. And that’s why lenses and prisms need to be coated.

The function of the coatings is to prevent light from being reflected. High-quality, multi-layer coatings can reduce the reflections to 0.25% of the incoming light, or even less; this will significantly improve the quality and brightness of the image. You want binoculars that are described as “fully multi-coated”, that is, all glass surfaces are coated with multiple layers. “Fully coated” means that all surfaces are coated, but not all (or any) have multiple layers, while “multicoated” means that some surfaces have multiple layers, but some have nothing.

A quick way to check for coatings if you have the binoculars in your hands: look at the reflections from the ceiling lights on the objectives. You should see several faint reflections, but none of them should be white. White reflections indicate the presence of non-coated surfaces somewhere in the optics; avoid instruments with this. Also, avoid “ruby coated” binoculars; the reflect large amounts of light and distort the colour of the light that does get through (the image will look greenish).

Focusing

In short, you need binoculars that allow you to adjust the focus differently for each eye; this can take the form of individual adjustment selectors for each eyepiece or a single central focusing selector with a separate adjustment knob for the right eyepiece. Either of these is acceptable, and mostly a matter of preference (but make sure that you can adjust for eye differences; this is important). Binoculars with individual adjustments for each side tend to be more resistant to water infiltration, but that will depend mostly on the quality of the instrument.

Field of view

This is the amount of sky you can see through your binoculars at a time. For astronomy, the wider, the better, up to a point: if the field of view is too large, you will get distortion near the edges of the image.

The field of view can be expressed in degrees or in “feet at 1,000 yards” (which refers to the width of the image you see). In metric countries, sometimes you also see “meters at 1,000 meters”. You want something in the range of 5 to 10 degrees, which is the same as 260 to 520 feet at 1,000 yards, or 90 to 180 meters at 1,000 meters.

This measure is strongly related to magnification; the larger the magnification, the smaller the field of view.

If you wear eyeglasses

Some binocular features are interesting for people with eyeglasses; one of them is called “long eye relief”. Eye relief is the distance from the eyepieces at which the image is in focus; that is, it tells you how far away you can be from the binocular while still being able to see the image. For eyeglass wearers who intend to use the binoculars without taking their glasses off, this needs to be long, in the vicinity of 20mm.

Also, ensure that the instrument has retractable or fold-down eye cups, so that you can get the eyeglasses close to the eyepiece without the cups getting in the way.

That said, I personally prefer to take the glasses off and use the binocular with the eye cups up. It is more comfortable for me, and it makes it easier to keep the image forming in the right place (with the glasses on I found it too easy to move my pupils out of the image). Unless you are very near- of far-sighted, you will see everything in focus with or without glasses.

Conclusion

To sum things up, you will want binoculars with:

  • magnification not lower than 8x and not much higher than 10x (and definitely not higher than 12x if you don’t want to use tripods)
  • aperture not smaller than 40mm and not much larger than 50mm
  • exit pupil between 5 and 7mm
  • fully multi-coated optics
  • independent focus adjustment (either one control per eyepiece, or a central one with an extra adjustment for the right pupil)
  • field of view of 5 to 10 degrees
  • and, if you wear eyeglasses, long eye relief and retractable eye cups

And, finally, you want to test the binoculars before you buy them. Hold it in your hands, make sure that it is solidly built, make sure that it is not too heavy to hold for long periods of time and so on. Repeat this with several models, see how they feel in your hands, see if you can perceive differences in the images. Prices can vary a lot; try to test both cheap and expensive models. Give preference to stores that cater to amateur astronomers instead of retail camera or general stores (that is, do not buy binoculars from Walmart unless you know what you’re doing). Also, read this page and do everything it tells you to. Good luck, and clear skies!

(for the record, I bought an 11×56 binocular from Aquila Optical, in Sydney, and I’m quite satisfied with it)

Choosing binoculars – part 1

For a novice amateur astronomer, binoculars may be very useful as a first instrument for several reasons: they are relatively inexpensive, have a large field of view and show images “right side up” (which makes finding things in the sky easier), are easily portable and require little to no setup. For more experienced amateurs, they may still be useful for most of the reasons mentioned above, even for those who have (or have access to) more powerful instruments. So, how do you pick good binoculars for amateur astronomy?

Binoculars are basically two small telescopes mounted side-by-side, with a set of internal mirrors and prisms that cause the images to be seen right-side-up and non-mirrored. There are two “models” of internal prisms: “roof” prisms are those used in “straight” binoculars, in which the objectives are exactly aligned with the eyepieces and the optical tube is straight, while “Porro” prisms cause the objectives to be more separated than the eyepieces and the optical tube not to be straight (that is the format that most people think of when thinking of binoculars). Functionally there is almost no difference between the two models, although Porro models tend to give you a wider filed of view, while roof models can be more compact than Porro models (and tend to be more expensive).

Binoculars are primarily identified by two numbers; for example, 7×50 or 10×40. The first number denotes the magnification achieved by the binoculars, while the second is the size, in millimetres, of the objective (front) lenses. Both numbers are important, and are a good starting point to pick the best possible instrument.

First, magnification, or power. That indicates how much larger an image will appear than if you were just using your eyes. It may seem that the larger this number is, the better, but that is not necessarily so. For astronomy use, unless you intend to use a tripod, magnifications between 7 and 10 are the most indicated. Anything over 12 will cause the image to shake way too much, unless the instrument is stabilized (by a tripod, for example).

Now, lens size, or aperture. The reason this number is important is that it tells you how much light the instrument gathers. Binoculars not only magnify the objects you’re seeing, they also act as larger light receptors than your eyes. Your pupils, when you’re in a dark location and fully adapted to the light conditions, will have a diameter of between 5 and 7 millimetres (the younger you are – as an adult -, the closer to 7mm it is; as you get older, it gets smaller). Since the light gathering ability is defined by the area of the objective, a 50mm binocular will gather over 50 times more light than your naked eyes. This will increase your limiting magnitude by around 4, under dark conditions (from 6 to 10, for example).

As a general rule, any aperture smaller than 40 millimetres in useless for astronomy; you simply will not get enough light into your eyes. 50 is a good size; anything much larger will be, well, too large and too heavy for comfortable use. It will be significantly more expensive, as well.

Power and aperture together define another interesting measure: the exit pupil. That is the size of the image that is formed on the eyepiece and that, ultimately, is delivered to your eyes; you can get this size by dividing the aperture by the magnification power (for a 7×50 binocular, the exit pupil will be 50/7 = 7.14mm). Ideally, this should be exactly the same size as your dark-adapted pupil or very slightly smaller, so that your whole pupil is used in collecting light and no light is wasted. Since pupils are not all the same size, this is clearly impossible; you should shoot for an exit pupil in the range of 5 to 7mm.

In the next article, I’ll talk about lens coatings and quality, focusing, field of view and considerations for people who wear eyeglasses (such as myself), closing with some tips on what to do once you are at the store.

Observations

Or, diary of a novice amateur astronomer, part 1.

I have recently started giving more attention to something I’ve been interested in for a long time: astronomy. Part of this included being a little more “hands on”; that is, not only reading about it, but also going out there and doing something. Which, in the case of astronomy, means observing.

In my particular case, I am disadvantaged by the fact that I live in the middle of a large city. Not only is my field of view severely limited by tall buildings (and the lack of a backyard), but also light pollution effectively hides from view everything but the brighter bodies (so much so that it is almost impossible to identify constellations; the limiting magnitude from my place is very close to 0).

magnitude is a measure of brightness of celestial bodies; the lowest the magnitude, the brighter the body; Sirius, the brightest star in the sky, has magnitude -1.44; the magnitude doesn’t change with time for most stars, but does change for variable stars as well as for planets, asteroids and other solar system bodies

limiting magnitude is the highest magnitude for which bodies are visible in a particular location (and viewing with a particular piece of equipment, if that’s the case); for locations away from any light sources (“dark sky” locations), the naked eye limiting magnitude is usually around 6 for most people

In any case, one of my first steps into the observing world (or universe) was joining the Astronomical Society of Victoria (ASV). Apart from monthly general meetings, the society also has several special interest sections that meet regularly. It also makes available to members some observing facilities: a small observatory in the suburbs of Melbourne, a dark-sky site in country Victoria, portable telescopes for limited-time loans and some limited access to the historical observatory located at the Botanical Gardens. There are many benefits, such as a subject-specific library, but probably the best one is the contact with other similarly interested people.

The second step, in a way, was to acquire some observing equipment. I’m too much of a novice to be trusted with a decent telescope, and I didn’t really want to spend money with a cheap one (since I don’t plan on being a novice for too long, and I’d want a better one very soon). Binoculars, on the other hand, are reasonably inexpensive, easy to operate, portable and very good for beginners. I’ll write about how to choose a binocular in the next article.

Now, I started this blog intending to write, at least at some level, about subjects related to software development (hence its title). I even did that, every now and then, and still plan on doing. So, if that’s what you look for, don’t despair: it will show up. Possibly even with an astronomical inclination.

Speaking of Mars…

Just as on Earth, the southern hemisphere winter is arriving on Mars; the autumn equinox was on 22 January, and the winter solstice will be on 08 August (there’s a very good table of Martian seasons here). Differently from Earth, though, the Martian winter lasts for six months (in fact, the southern winter is almost one month longer than the southern summer), and this has strong implications for the Mars rovers Spirit and Opportunity.

Both rovers are in the Martian southern hemisphere, but Spirit is much farther south, at a latitude of around 15 degrees (Opportunity is closer to the equator, at less than 2 degrees south). This means that, during the long Martian winter, Spirit will receive much less sun light than it is used to, and this, in turn, will affect the amount of energy it will have available to function. For this reason, NASA spent the last few weeks trying to take Spirit to a safe location where it could park for the winter in a slightly northern inclination.

Last weekend, after spending some time almost stuck in a sandy area, Spirit arrived at such a safe location and is now parked with a Sun-facing tilt of 11.5 degrees; this has already bumped its power reserves up by more than 20%, and it is likely that the rover will remain at this location for the whole winter.

Spirit had such a problem with that sandy area, in part, because one of its six wheels has stopped working weeks ago and is being dragged around without spinning. This increases the rover’s power consumption and affects its ability to negotiate the Martian terrain. Still, both rovers are in excellent shape, and have already exceeded their “warrantly” by over 700 (Earth) days.

Venus Express arrives

Venus Express, the ESA‘s sister mission to Mars Express, arrives today; the orbit insertion maneuver starts in a few hours (just after 5pm Melbourne time, 7am UTC).

The ship is basically an upgraded version of Mars Express, minus the ill-fated Beagle 2 lander. It was launched in November of 2005, and the expected duration of the mission is of two Venusian days (that is, some 500 Earth days). It will study in detail the Venusian atmosphere and try to image (through the cloud cover) the full surface of the planet. There is much our scientists still don’t understand about the Venusian weather and erosion patterns, and this mission will try to find some explanations. Differently from most Martian explorer satellites, Venus Express will settle into a highly elliptical orbit, ranging from a distance of 250 to 66,000km from the planet.

As with Mars Express, one of the main sites on Earth receiving data from Venus Express will be the ESA ground station in New Norcia, Western Australia. New Norcia is more famous for being centered around a monastery (it’s “Australia’s only monastic town”), but it was already advertised as being the first place on Earth that would hear about news of life in Mars. There’s no such expectation for Venus, of course, but New Norcia (and Australia) continues to play an important role in space exploration.