WISE - watch the skies!

[Retired_for_now]

The latest space observatory, the Wide-field Infra-red Survey Explorer went up on 14 Dec. WISE is different in that it has an extremely wide field of view and a very high resolution detector cooled by 35 pounds of solid (ice) hydrogen. It's primary mission will last 6 months, though it should have a 10 month supply of coolant (and it, like the Spitzer Telescope, will still be usable though less sensitive after the coolant is exhausted).

Why should you care? In addition to cueing the planet finders (COROT, Kepler, James Webb), WISE will be able to locate and provide the first good estimates of the population of Earth-crossing comets and asteroids - you know, the planet-killers.

Anyway, found the WISE-is-a-box model from Berkeley while Google-cruising at WISE - Education & Outreach: Classroom Lessons (http://wise.ssl.berkeley.edu/education_class.html) . Not much there. However, the box does provide a scaled six-view drawing of the spacecraft. Happy, happy! Joy, Joy!

A little work importing and scaling the pictures on the box and we're ready to draw. Like all spacecraft, the structure is composed of flat, conic, and spherical surfaces (streamlining is not a factor). Using the scaled pictures, you can draw the required boxes, cylinders, and conics directly over the relevant picture. This has the added advantage of allowing you to extract dimensions (properties of the box, circle, shape you drew) for model parts without having to squint at the ruler. This makes doing the pi for the cylinders and conics much easier - and reduces fit problems.

WISE consists of and upper cooled optical section (cryostat), an octagonal bus, and various supporting bits for power, comm, and guidance.

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I modelled the upper section as a cylinder with upper and lower tapering conics. The interior optical section was modelled with a simple cylinder and a spider supporting the secondary mirror. You could omit the internal optics and just cap the cryostat. Like all paper models, most of your time is spent creating the parts (scoring, cutting, bend/folding, and gluing up little bits).

First page (3 total) of bits
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Secondary mirror spider
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Optical barrel
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[Retired_for_now]

The optical barrel is finished off with the top of the cryostat. The entire assembly can then be inserted into the cryostat cylinder (when I get that part done).
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Other little bits get done as the mood strikes me. The star trackers are conventionally modelled as a cone atop a cylinder. The triangular brackets mount them to the bus.
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Meanwhile, constructing the struts to connect the cryostat with the bus was an interesting challenge. I went through about seven different iterations before I got something that captured the look of the casting (U-channel with lower angled attachment block) and was reasonably buildable. I heeded the advice of the PM brain trust and designed actual struts - with small attachment tabs that will fold in toward the center of the strut to mimic the actual attachment method.
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Yogi

[Texman]

Fascinating. Glad someone is taking this on.

[Retired_for_now]

Thanks Ray.

I started with a simple U-channel for the upper strut bracket with the struts attached to the sides. This makes a fairly strong connection and leaves enough flexibility to position the strut during assembly.

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Actual attachment on the spacecraft uses a center pin on the strut fitting into an angled block at the bottom of the bracket. So, variant 2 models the attachment plate and the angled block with small tabs. I didn't use this one, just doesn't look strong/stiff enough.

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The current bracket uses the u-channel with double thickness side plates from my first effort and two tabs at the bottom that are cut free and bent inward. The strut's tabs then bend inward toward the center so the final attachment is in line with the strut axis. The little tabs on the strut aren't very strong, but all eight provide a surprisingly strong structure to hold the cryostat in place. The tabs, especially the long one at the bottom of the strut, provide enough flex and slop to allow assembly and adjustment if needed.

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Yogi

BTW: anyone who'd like to do a test drive of my directions, drop me a PM with your email and I'll send you the files. Price is that you post a picture of your finished model (and any other photos of interest - not that I expect problem areas, HAH). Improvements and add-ons encouraged.

[SAustin16]

Thanks for putting things in perspective, Yogi.

Great model build. You're doing a fine job as usual.

Merry Christmas!

[cdavenport]

Yogi, thanks for the info on WISE. Isn't NASA also planning a specialty satellite to look for Earth-like planets? Astronomers have been using mostly indirect methods thus far, but have been able to image a few Jupiter-sized planets.

I got the impression that the next gen satellite is going to be able to image smaller planets.

[Retired_for_now]

Thanks Steve.

Charles - Several planet finders out there. The indirect methods (measuring planet induced stellar wobbles) are used by just about all observatories, space and ground. The Kepler Observatory (IR) that just went up will be looking for variations in stellar brightness caused by planetary transits - and may be able to pull spectra from those planets to check their composition, temp, etc. James Webb will do that mo-betta when it goes up. ESA just sent up a really big IR telescope, Herschel, also. Longer term projects mostly focus on interferrometers to pull spectra, not images. And for my final stunt - Hubble has actually take a picture of a planet - NASA - Hubble Directly Observes a Planet Orbiting Another Star (http://www.nasa.gov/mission_pages/hubble/science/fomalhaut.html)

Yogi

[Retired_for_now]

The WISE bus is an octagonal box (got some practice with Magellan, Voyager, Mariner 10 and IBEX). Straightforward job to fold/glue up the sides then close the top.
The solar panel (fixed on the spacecraft) is also a box, a bit more challenging since it's very thin. Key here is to have a clean, flat work surface and make sure the box stays flat against the surface as you glue it up.
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Below the bus is a circular plate edge glued to a conic and capped with the thrust ring and bottom.
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The high gain antenna is a flat, phased array (now standard, no more big dishes on space probes I guess). It's just front and back faces joined with a tabbed edge band.
Got around to the cryostat, finishing the cylinder, top and bottom conics and the bottom. Then, the optics and top plate are glued down followed by the sunshade. The shade is two nested conics to provide inner and outer printed sides. The shade is edge glued to the top plate. It's cut after assembly to get the angle on the top edge.
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With the big pieces done, it's time to finish the little bits. WISE is actually a fairly simple spacecraft by design. Two star trackers and a magnetometer (part of its attitude control system along with 4 gyros and three magnetic torque rods - the rods react against the Earth's magnetic field to periodically unload the gyros) are all there is for greebles.
The only really intricate task is building up the cryostat attachment struts and connecting them to the bus. I built up all four strut/bracket assemblies, then attached them to the cryostat.
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Yogi

[umtutsut]

Can't wait until you publish this one, Yogi! Of course, I'll add/subtract/multiply/divide, just like with the LCROSS-Centaur! :p

(BTW, made some good progress on the latter the last couple days. Pix soon!)

:cool: Les (Friendly Airplane Asylum & ex-NASA flack)

[Phil]

Looking on with extreme interest! Beautiful work Yogi!!!

[Retired_for_now]

Thanks Les, I will give the Berkeley mission folks first chance for posting it (if not it goes up here and at the LHVCC).

Thanks Phil - glad to have you out and about (you went quiet for a while - missed your wit and insights).

Buildup continues - fastened a few bits to the bus now (brackets for the star trackers and low gain antenna under the HGA disk), things that require a little squeezing to attach. The struts will attach at the dots on the corners of the bus.
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Time to attach the cryostat. I started at a random spot, applied a dot of glue to the spot on the bus, then pressed down the bent end of the long lower tab on the strut. I worked in sequence (clockwise - right handed, see) to glue each strut. It's really floppy and requires some careful handling until you get four of the struts down. Then, stiffens up fast. You WILL need to use a tacky, fast setting glue to do this (go Titebond II). The final connection is eight little card tabs - surprisingly strong.
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I tried to keep everything consistent as I glued the struts, but found that it seemed to naturally set up its alignment if you're reasonable careful. There's enough flex in the connections for the struts to allow you to maneuver them into position without dragging everything through the glue.

With the bus connected to the cryostat all that remains is to attach the HGA and solar array. The HGA sits on four little posts glued to one face of the bus. The associated LGA then glues to the post on its mount below the HGA.
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The solar array mount is a cylinder that attaches to the bus face opposite the HGA. It helps to block up the bus assembly so you can use your flat work surface to attach the solar array square and aligned with the rest of the satellite.
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Star trackers and magnetometer assembly are attached - and there you go.
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Yogi

[Retired_for_now]

This is the point I usually stop when designing and building. I strive for an accurate basic structure and as much detail (graphics) as I have time for. I should spend more time hunting up textures - but the solid colors work OK for educational purposes. Educational models also need to be fairly robust (though I usually make two when the request is for a vis-aid; one to handle regularly and a spare for when the first gets broken). Graphics aren't (usually) breakable.

For the detailers out there (we all know who you are - and are constantly drooling slack-jawed at your work/artistry/focus) the basic structure and graphics provide a foundation for adding fine detail.

Some thoughts for WISE -

Magnetic torque rods (see above) can be simple lengths of wire glued over the graphics or can be elaborated with brackets and wiring.
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The (graphic) wiring can also be added up to the point you run out of patience and references.

You can use gold foil, small mirrors, etc. to enhance the optics.
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Biggest opportunity on WISE is to add on the cooling manifolds and piping. I've limited this one to graphic/block manifolds and graphics for some of the pipes.
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Second prototype (was still working on brackets - I don't have Bomarc's skill on cutting out and replacing so I usually just make another one so long as the parts count is reasonable). I tried cutting some thin strips of card to add 3-D to the piping. Not totally successful. Bomarc's (and others') technique of using thin solder-wire would work better.
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With pipes added, it would be best to bulk out the manifolds and connections with boxes and cylinders, using the pictures for reference.

Additional work could be done on the struts and brackets to bulk out the bracket castings and model the struts better. Ideal strut would have a center pin at each end and "socket" into the upper bracket and a lower bracket (more enhancements - hmmmmn - I could do a graphic fix for the lower fitting ...)

You can also add detail for the sides of the bus. The graphics depicted are actually panels recessed below the insulation on the rest of the surface so you'd have to cut out the graphic and re-install from the inside (or add a layer of insulation to the outside with a cut-out to reveal the graphic). There are also a few handles in a couple of spots.

Anyway ....

[Retired_for_now]

And the 1:48 scale version for the Planetarium display case to match the spacecraft already there.
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This was a good place to use the alternate, glue-to-card struts. Too many tiny tubes already...

Yogi

[tazman3]

Yogi, that is so tiny, yet so awesome! Great job!!

[Retired_for_now]

Thanks Tazman.

The "alternate" strut design
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Display setup.
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So, pending delivery to the Planetarium, that should be that.

Yogi

[Ashrunner]

Excellent work, Yogi. You're rebuild of WISE is exceptional. I'm sure it will be a valued addition to the Planetarium's collection.

[Retired_for_now]

Thanks Ashrunner,
Now we just wait on the Berkeley mission team to see if they'd like to use it. If not, I'll release it here and at Lower Hudson Valley. Meanwhile, there are a few more interesting and/or operational observatories up there ...

Yogi

[jparenti]

I'm hoping to get to building this one soon myself. I planned on it last week, but I got sidetracked by the dreaded H1N1 -- luckily I only spent a few hours in the hospital. (I wish I was joking. Get your shots guys!) :)

[Retired_for_now]

Whoa - glad to hear you're OK. Seasonal flu strains are also bad news - so second on getting the shots.

Yogi (a regular pin cushion and still picked up all kinds of crud around the world)

[Retired_for_now]

Just to close the loop - WISE is posted for download at the Lower Hudson Valley Challenger Center (jleslie48.com).

Yogi

[lancer525]

Bravo, Yogi!

Another excellent design from an innovative designer, of a really cool spacecraft!

[lunger1]

I just downloaded it and can't wait to start the build!!!