Archive for May, 2010

What you need to know: Japan is launching two satellites on May 18th, 2010, one towards Venus and the other, IKAROS, to demonstrate the tranquil and romanticized method of interplanetary travel: the solar sail. A solar sail is unpowered, the spacecraft pushed by the force of the solar radiation. A solar power sail combines thin solar panels with the sail for on board power.

Edit 5/17 5pm PST: Launch scrubbed due to weather. The window is open until June 3, other wise Junya Terazono suggests that it may be launched in May 2011. No official word on any of that yet though.

Emily on Twitter
Edit 5/17 11:45pm PST: Launch rescheduled to May 21 6:58 (Japan time).

The JAXA/Akatsuki Twitter account (you might need THIS)

Edit 5/22 IKAROS launched successfully and powered up!

Solar Sails

Sounds like science fiction, but a solar sail is pushed by the photons from the Sun. That’s right, you’re using sunlight to sail, not the solar wind. The Planetary Society has a full explanation, but  when a photon is reflected it exerts a small force on the surface reflecting it. The Sun certainly generates a lot of photons, so if you have a large, lightweight, reflective surface, it will be pushed by the force of many photons being reflected off it. Just like a sailboat, the larger your sail the more wind (or in this case reflected photons) you can catch.

And therein lies the problem. Photons are very small. Very, very small. Imagine an regular ant trying to push a semi-truck. Not gonna work – though in a perfect situation there would be some small effect. How many ants do you think you would need? Would all those ants be able to push on the truck or would there be too many of them? A solar sail needs to be huge, and extremely lightweight.

IKAROS

JAXA and The Planetary Society are both done with solar sails being relegated to science fiction just because of the technical challenges. JAXA’s decided to combine a solar sail with solar in order to demonstrate some of the possibilities awaiting us. Their “sail” is covered in solar panels, so in addition to being pushed by the light from the Sun they’ll be generating power. The main mission objectives: prove that a spacecraft can be propelled by a solar sail, and prove that the thin solar panel membranes they’ve chosen do generate power.

Ikaros will unfurl its sail by spinning. You can see this in their video, the spinning starts around 06:50. The video is in Japanese, but you don’t need to understand what they’re saying to want an umbrella that works this way!

Daedalus and Icarus

Daedalus was imprisoned in a tower with his son Icarus, so he built a pair of wings for each of them. The feathers were fastened to the frame with wax, so Daedalus warned his son not to fly too close to the Sun. Of course, being a young boy Icarus ignored his father. He flew so high the wax melted, the wings broke, and he tumbled to his death in the raging sea below. Daedalus escaped successfully and lived safely for a while after that.

That’s the myth as I’ve heard it – I think I’d prefer to name my test mission after Daedalus.

Questions I had after reading about IKAROS:

• Does IKAROS have an ion engine? No, that’s an application of combining solar sails with other propulsion that JAXA’s website proposes.
• Is IKAROS going to Venus? Well, it’ll be on a trajectory towards Venus, but it won’t be able to do orbit insertion so it will just do a far-away fly-by.

Want More?

IKAROS at JAXA

JAXA (the Japanese Space Agency)

The Planetary Society’s Light Sail

~ A l i c e !

Stuart Atkinson is hosting this week’s Carnival of Space over at Cumbrian Sky. He’s got some very flattering things to say about my Iapetus story (don’t believe everything you hear from him about me, he’s entirely too generous!)

Oh, and don’t forget your blue/red 3-D glasses …

~ A l i c e !

Let me quite briefly draw your attention to the tab in the upper left corner “Seattle Stargazing” (for those of you reading through RSS, the link will take you to the same place) where I recommend good locations near and in Seattle for urban and not-so-urban stargazing.

I’m getting ready to update it for 2010, but the recommended locations remain the same. If you’re clicking over here from Greg’s Seattle Astronomy Examiner article – that page probably has some places to interest you.

~ A l i c e !

Which missions do you wish people wouldn’t forget about? Here are some of mine:

• Apollo 11. Humans first walked on the Moon. 2 American men: Neil Armstrong and Buzz Aldrin. Michael Collins piloted.
• Sputnik. First man-made object in orbit – a beeping satellite from the USSR.
• The Vostok Program: Yuri Gagarin – first human in space, first human to orbit the Earth. USSR.
• Mercury (specifically “Freedom 7”): Alan Shephard – first American in space.
• STS “Space Transport System” – the official name of the Space Shuttle program. Many important occurrences.
• Pioneers 10 & 11, Voyagers 1 & 2 – Our first “close” views of the other planets.
• Hubble – Hubble’s photos changed the average person’s view of astronomy, and advanced the science immensely.
• Skylab, MIR, and ISS – these are some of our space stations, we had them serially not simultaneously. ISS is the only one now.
• SpaceShip One: Burt Rutan flew the 1st commercial (non-government/non-military) flight into space on a reusable craft.
• Last but not least, keep these in your heart: X-15, Soyuz 1, Soyuz 11, Apollo 1, Challenger, Columbia.
• Just a couple inspiring names: Sally Ride, Valentina Tereshkova, John Glenn, Shenzhou

Links

• Want more?
• Disaster Details
• If that link doesn’t work – use this one. Or the source.

~ A l i c e !

By now my second podcast for 365 Days of Astronomy should be live, and here is the post to support it – containing links I mentioned in the podcast. So go listen already!

In this podcast I tell a story about Iapetus and the mystery shrouding her. And yes, I mean tell a story. I was inspired by Jay O’Callahan and his fact-tales.

By the way, this is the only thing I’ve put out on the internet that I haven’t licensed under Creative Commons. (Things that aren’t mine, but are posted by me may be excepted as well. For example, NASA retains the rights to their images though they allow generous usage of them, Jason retains the rights to his photographs, and there are others). I do, in fact, hold the copyright on this story. I’ve granted 365 Days of Astronomy the rights to replay it – and you can replay it as well and use it for personal and educational purposes, but don’t claim it as your own. Let me know if you want to use it for something else, I’ll probably says yes and be flattered.

Want More?

Emily Lakdawalla about Iapetus

NASA’s Cassini Homepage

The Story

Once upon a time there was a moon named Iapetus. She orbited Saturn at a distance of over 3 and a half million kilometers, and there were only two larger moons of Saturn, but still all the other moons made fun of her.

They made fun of her because her front hemisphere was a lot darker than her back hemisphere. This darker area was called the Cassini Regio, but the other moons laughed at her and said she looked like a spherical Oreo. Iapetus thought this wasn’t really fair, since she wasn’t even spherical herself, more lumpy in places.

One July, the Cassini Spacecraft showed up. He noticed how the other moons wouldn’t let Iapetus play with them, and how they always made fun of her. “Come over here, Iapetus,” he said, “I have a story to tell you.”

“Me?” asked Iapetus, “You have a story to tell me?”

“Yes, but only for you, your other friends don’t get to listen to this story.”

Suddenly the play-space became silent. The other moons stopped their games, their hula-hoops fell off, the ones running on the track slowed down, and they all turned around to look at Cassini and Iapetus talking quietly as they orbited around Saturn.

“Once upon a time there was a moon named Iapetus,” started Cassini.

“No, no! We already did that part, Cassini!” protested Iapetus, “get to the good part!”

“Well,” said Cassini, “the first time anyone from Earth saw Iapetus was in 1671, and that man’s name was Cassini.”

“Hey, that’s your name too! Wait, which one is Earth, is that the third or the fourth one out from the Sun?” asked Iapetus.

“Fourth, silly!” said Titan, one of the other moons, stepping closer to Cassini. “Don’t you know anything?”

“I’m not silly!” yelled Iapetus.

“Titan, Earth is the third one. Now if you’re going to listen you both need to sit down and be quiet like Phoebe,” said Cassini gently. “Back then no one knew what mysteries awaited them on the surface of Iapetus.”

“See? I’m not silly, I’m mysterious!” said Iapetus, sticking out her tongue at Titan.

“Shh! No more interruptions.” Cassini frowned at the two of them.

“Since Voyagers 1 and 2 first glimpsed Iapetus’s interesting surface there has been much speculation by scientists all over Earth about how Iapetus came to be this way. I will tell you a few of these ideas, and then Iapetus can tell us what really happened.

“The first idea involves Phoebe. Where is Phoebe? Ah, there she is. A scientist named Hamilton proposed that micrometeors could have knocked some dark dust off Phoebe, then Iapetus could have swept up this material such that it all collected on the front hemisphere.”

“But Cassini, I’m a different color than either Iapetus’s dark side or Iapetus’s light side. I don’t think we’re related!” protested Phoebe.

“Yes, that’s a problem with this idea, as the Earth scientists found out in 1998,” said Cassini.

“What about me?” asked Hyperion, “I’m close to Iapetus too, maybe I’m part of this.”

“That was the very next idea I was going to mention, Hyperion, thank you for bringing it up. There are two different theories relating to you. The first thing though is to find out if the dust can actually get from Hyperion to Iapetus. The scientist Marchi and his colleagues think that’s pretty easy, but how do you get the dust off Hyperion in the first place?”

“Hit it with something!” chorused all the moons of Saturn, making a terrible racket and almost waking the Sun up from her mid-afternoon nap.

“I see you know the secret,” agreed Cassini. “If you need to get something from one place to another in the Solar System, you usually need to slam two things together.”

“And look,” said Hyperion, holding his arm up next to Iapetus’s dark side, “we’re basically the same color on this side of Iapetus.”

“So you are,” observed Cassini. “That makes this idea seem plausible. One last puzzling idea is that perhaps this dark material is from somewhere else, and was collected on both of you.

“One of my jobs in coming here is to take a better look at you Iapetus, and see if I can provide any useful data for the scientists to use in figuring out where your Cassini Regio came from. Do you know the answer?”

“Wow, everyone’s looking at me?” asked Iapetus, “I dunno, I can’t remember when it happened. I am pretty sure that the light side of me is ice, because my backside is always a little chilly. Anyway, if I did know where the dark stuff came from, shouldn’t I leave it as a puzzle for you to find out?” With that she ran off to play hula-hoop by herself, but Hyperion and some of the smaller moons followed her and they all started a game of Occultation.

The End

~ A l i c e !

The ‘cast