SPIDER is preparing for launch!

Follow the progress of the team as they prepare to launch SPIDER.

Watch via live-streaming here.

SPIDER screen shot

The SPIDER team loads the instrument onto the launching vehicle.

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SPIDER emerges into the sunlight

Zigmund Kermish

Zigmund Kermish

Last week was an eventful one for SPIDER, myself, and for the Long Duration Balloon (LDB) facility here in Antarctica. The first launch of the season happened this Thursday, with a beautiful launch of the first of the three balloon-borne instruments that are launching from LDB this year, ANITA. The shuttle schedules and my shift schedule made it so I wasn’t at LDB during launch myself, but many of my colleagues were there and able to get some excellent photos. See the animated gif below I made from John Ruhl’s photos.

ANITA balloon launch

Animated GIF of ANITA’s launch (photos by John Ruhl). The winds changed direction after the balloon was already laid out on the launchpad, so you can see the Boss (vehicle) driver had to make a quick correction to end up with a beautifully smooth launch.

The next morning, I took part in a video chat with the 3rd grade classes of Hoover Elementary in Palo Alto, CA. Thanks to my friend Ms. Elsa Chen for setting it up. The students had some excellent questions and seemed pretty excited when I showed them our telescope and the view of Mt. Erebus outside our door. I had a great time talking to them and I hope they enjoyed learning a little bit about our work and research life in Antarctica.

Video-chat with students

Video-chat with students

Since one of the students asked how long it takes me to get to the lab, I figured I should post a video I made a while back of the drive out to LDB (condensed from the 45 minute drive to a 3 minute time-lapse video).

SPIDER also made some great strides to near flight readiness this week. We installed our ‘wall of power,’ a four by six array of light-weight solar panels that will keep our batteries charged in flight. We then rolled the instrument outside to test the solar panel array throughput and looked at the Antarctic sky for the first time through our telescopes. Of course, with all that progress on integrating the systems, we discovered yet more issues and bugs to fix, but that’s to be expected. We’re making lots of progress on all the issues we’ve uncovered, so we’re hoping to be on schedule for a launch soon enough!

SPIDER, nearly ready to leave the hangar

SPIDER ABB (All But Baffles…and a few other finishing touches) in the highbay. The solar array on the right of the photo is the big addition. This was also the first time this campaign we’ve had all 6 telescope apertures open to the room, in preparation for looking at the Antarctic sky. We usually close them off with curved metal plates to reflect light back into the telescopes for lower loading and to shield the detectors from radio-frequency interference (RFI) found in the room.

Rollout of the solar array

SPIDER ABB rolled out onto the deck of our highbay, getting some sunshine for the first time! The reflections off the aluminized mylar sun shields is pretty intense.

Rollout of SPIDER

Another view of SPIDER ABB on the deck, showing the highbay behind it.

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Nearing flight readiness!

A balloon-borne instrument getting ready for launch.

A large vehicle known as “The Boss” will carry SPIDER to the launch pad on launch day. Pictured is another balloon-borne instrument called ANITA, which is on the Boss for its hang test. Mt. Erebus is in the background.

Zigmund Kermish

Zigmund Kermish

It’s been an exciting week here on the Ice. The other two experiments here with us, ANITA and COSI, have declared themselves ‘flight ready’ and gone through compatibility testing with a hang test on the launch vehicle. That means the science teams are pleased with the functionality of their fully integrated instruments, and NASA’s Columbia Scientific Balloon Facility is happy with how the experiment interacts with their equipment. So now they wait for a launch opportunity.

The circumpolar wind pattern, in which the wind blows clockwise around the South Pole, has set up as of about last week, but flight opportunities only occur when the weather is just right. It’s a bit of a Goldilocks-like situation: there have been four scrubbed launch opportunities over the past week because the winds were slightly too strong, or there was a weather system coming in that was deemed too risky. Moods have been swinging wildly as a possible launch opportunity (often, with an early morning start to the day) turns into a scrubbed launch. Hopefully, ANITA and COSI will launch soon. The longer their flights are delayed, the bigger the risk for us in getting a good launch window.

“The Boss” is the launch vehicle here at the Long Duration Balloon (LDB) facility. The Boss is an impressive piece of machinery that hoists the payload, will drive it to the launch pad on launch day, and then drive around with the payload to follow the balloon’s initial trajectory and help guide the payload for a smooth start. COSI and ANITA both had their hang tests with the Boss over the past few weeks.

The timelapse video shows the very first scans of SPIDER in the highbay here in Antarctica. The video captures the entire system, from the pivot, ropes and spreader bar up at the very top, to the reactional wheel spinning at the bottom. The time-lapse give a false sense of speed to the smooth, slow and steady scanning that occurs in reality. In addition to the back-and-forth motion in azimuth, you can see very small motions in elevation.


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Antarctic “Adventures”

Johanna Nagy

Johanna Nagy, graduate student, Case Western Reserve University

Although this may be a harsh continent, I can’t exactly pretend that my lifestyle down here has been difficult or uncomfortable.  I spend most of my day in a heated and well-equipped lab space.  I live in a dormitory with heat, electricity, indoor plumbing, and Wi-Fi.   I have three hot meals cooked for me every day and I am transported to and from work by a motorized vehicle.  There are much less remote parts of the world that do not enjoy these luxuries.  Clearly life in Antarctica is not what it once was.

On the other hand, when it’s time to take a break from the lab, there are some incredible opportunities to leave town and explore the local terrain.  While we stay on marked trails where there is no danger of getting lost or falling into a crevasse, I can let my imagination run wild where I cannot.  I am an Antarctic explorer.  My quest is to reach the top of a peak, explore new terrain, or conquer an ice labyrinth.  If I survive this adventure, I know another is waiting for me just around the bend.  So far I’ve scaled miniature mountains, observed a smoking volcano, and wandered among icebergs and lived to tell the tale.  There is even photographic evidence.  Hiking has become my favorite pastime here, and it is so exciting that the cold is tolerable.  Everything that I have done is within a few miles of where I live and work, so I have not even begun to experience what this continent has to offer.

Some people might think that there is not much to see down here.  Isn’t it just snow, ice, and rock?  Well, yes, but it’s not that simple.  In the absence of most plant, tree, and animal life the landscape takes on a life of its own.  I have the same 40 minute to and from lab every day, but it looks different every single time.  The light changes, the snow drifts, the wind transforms the environment, and the pace of change is not so glacial.  In Antarctica, more than any other place I’ve been, it feels as though you really can’t see the same view twice.  It’s a new and different experience every time, and it makes me want to see more.  The snow is so bright and the rock is so dark that the contrast in the scenery is severe.  But when you look at the black and white world for long enough, colors begin to emerge.  There are so many different shades of white that paint stores have not begun to create them all, and each is unique, and special, and beautiful.  There are subtle differences in light and shadow that bring about a change of perspective.  Even temperature gradients in the air change how things look.  No matter what adventure I have chosen here, there was always something to see, and it was always worth seeing.

The sheer number and variety of “adventures” that I have experienced so far in Antarctica has far exceeded my expectations.  I find myself falling more in love with this continent every day.  And when it’s time to give my imagination a break and have a real adventure, well, that’s why I do scientific ballooning.


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Putting SPIDER together

Zigmund Kermish

Zigmund Kermish

Zigmund Kermish is an associate research scholar at Princeton University.

To ship SPIDER to Antarctica, where it will be attached to a balloon and floated over the icy continent to search for signals from the early Universe, the researchers had to break SPIDER into pieces for shipping. They’ve spent the last few weeks putting SPIDER together again. Here is a recap:

Lots of progress has been made over the past few weeks in getting SPIDER put together. I’ve been a bit too busy to blog much, so here’s a short post with photos and commentary in the captions.

We assemble SPIDER’s two main subsystems, the “gondola” and the “cryostat” in parallel.

The gondola provides the structural support for the instrument, hanging points for the balloon, and pointing control systems that allow us to move the telescope in azimuth and elevation (the angles used to define the apparent position of an object in the sky, relative to a specific observation point).

The cryostat provides the very cold temperature needed and contains the guts of the experiment: six independent telescopes that will image the cosmic microwave background (CMB).

The cryostat takes about a week to cool down from room temperature to the very cold temperature of 4 Kelvin (-452 degrees Fahrenheit), leaving lots of time for the gondola assembly and testing of some subsystems before mating the two and starting to integrate the entire experiment. “The lift,” where we hoist over the 3000 pound cryostat (which is relatively full of liquid at this point!) to the gondola for mounting is a nail-biting milestone.

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A very SPIDER Thanksgiving

Jeff Filippini

Jeff Filippini

Jeff Filippini is a postdoctoral scholar at the California Institute of Technology.

In the SPIDER team this year we have a lot to be thankful for.  The major parts of our payload are assembled.  Our cryostat is cold and performing reasonably well.  All six of our half-wave plates (polarization modulators) are installed and turn smoothly at low temperature.  All six of our focal planes are at operating temperature (sub-Kelvin!) and the bolometers are functioning.  We have the privilege of living and working in Antarctica, one of the most stunning places on Earth.  Most importantly, we are here with a fantastic team, having a great time with one another in and out of the lab.

Thursday (Thanksgiving local time) was a normal work day on the ice, but our LDB (long duration ballooning) facility galley staff prepared a special treat: a full turkey dinner for lunch!  The food was exceptional, particularly the turkey (moist and delicious!) and the orange-cranberry sauce.  We all appreciated the taste of home.

Thanksgiving menu

Thanksgiving menu at the long duration ballooning facility

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Wait, why am I in Antarctica?


Zigmund Kermish

Zigmund Kermish

Zigmund Kermish is an associate research scholar at Princeton University. He blogs here.

I realized I’ve not yet written a blog post explaining why my experiment is in Antarctica. Things are temporarily quiet on the Ice while we’ve been waiting for the SPIDER cryostat to cool down, so now’s a good time to make the attempt.

To get the best results from SPIDER, we have to go to very high and dry locations. This is because water vapor in the atmosphere limits SPIDER’s sensitivity. There are currently two terrestrial locations that are commonly used: the Atacama Desert (where POLARBEAR and ACTPol sit at about 5,200 meters above sea level) and the South Pole (where the South Pole Telescope, the KECK array, and this year BICEP3 operate at 2,800 meters).

Of course, one can always go beyond terrestrial limits. With a big enough budget and enough time to develop the project, you can launch a dedicated satellite mission to eliminate the atmosphere all together, achieving dramatically improved individual detector sensitivities. Historically, satellite-based instruments have provided the definitive measurements of various aspects of the cosmic microwave background (the faint signal left over from the Big Bang), but they usually build upon the groundbreaking discoveries made closer to Earth. These discoveries have been made from the ground and from one other platform: balloons.

Balloon-borne instruments have one big advantage: they allow us to get above nearly all of the atmosphere, approaching the detector sensitivity of satellite-based instruments at a fraction of the cost of a satellite mission.

This increased detector sensitivity has two advantages: you can observe a larger fraction of the sky for a significantly shorter amount of time and still get a higher fidelity map than what you can do from the ground (observing for days rather than years) and you can observe in frequency channels that are difficult (if not impossible) to use from the ground. Both of these features, multiple frequencies and larger sky coverage, are necessary to ultimately demonstrate the ‘cosmological nature’ of the signals we’re looking for – to show that it’s not just a signal from some foreground in our local galaxy and that it has the required statistical properties across the sky we expect from proposed theories.

As shown in the below gif, SPIDER can observe a large fraction of the ‘clean’ sky (the white outline) for 20 days and get nearly the same sensitivity over that region as a ground based experiment like the BICEP2 project had on their smaller region (green outline) after several years of observation.


A map of the dust intensity seen in the sky, the bright center band the emission from our own Milky Way galaxy. The overlay that is fading in shows several things: The colored diamonds show the most recent data about the *polarization* strength of the dust signal, blue being less polarized dust, the outlines on the overlay show the regions observed (or to be observed shortly!) by BICEP2 (green), POLARBEAR (red), and SPIDER (white).

Ok, so that’s why we want to dangle our instrument from a balloon. But why Antarctica? Why don’t we just launch our balloon from New Jersey?

Well, for one, at some point, we need to bring the instrument back down to Earth, and that involves literally letting it fall to the ground so that we can recover it. That’s why scientific payload balloon flights only happen in places with low population density. In the US, payloads are flown out of Fort Sumner, New Mexico. They used to fly out of Palestine, Texas as well. Payloads flown out of these locations are limited to flights anywhere from a few hours to a few days because they eventually start getting too close to population centers.

Antarctica doesn’t have any population centers, so rather than being limited by distance, flights are limited by how long the balloons can stay afloat. Currently, that’s about 40 days. Beyond that, weather patterns setup circumpolar winds during the austral summer here.

So if you launch a balloon at the right time, it’ll come back close to where it started, making recovery of the instrument easier (it takes about a week to ‘boomerang’ back around). This is especially important for an experiment like ours since we need to physically recover our data off the drives that fly with the instrument. The bandwidth of in-flight communications limits us to only getting a small fraction of the data from the instrument during flight. One of the many ballooning challenges is to make the system as autonomous as possible so minimal human intervention based on the limited information we decide to ‘downlink’ to the ground is needed.

The other fundamental challenges of ballooning that make this a very different game from ground-based experiments I’ve worked on: weight and power constraints. Having to fly the batteries you need to power the experiment, the solar panels to keep them charged, the cryogenic system to keep the everything cool and all the readout and control electronics systems while still staying below the maximum mass limits current balloons can float makes a project like this a fun problem to solve. The absence of day-night cycles during the austral summer in Antarctica helps address the power and weight constraints by giving us a continual source of solar power. This means we only need to fly a few heavy batteries to provide a non-variable power source and we can dedicate more of our mass budget to the scientific instruments. More compromises have to be made when designing payloads to fly at mid-latitudes, where enough batteries need to fly to power the payload throughout the night. There are many advantages to these mid-latitude flights though: larger available sky and longer (100 day!) flights with NASA’s new, soon-to-launch-with-science-payloads super pressure balloon platform (SPB).

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Progress – SPIDER on the Ice

Anne Gambrel

Anne Gambrel

Anne Gambrel is a graduate student in the Department of Physics at Princeton University. She blogs at SPIDER on the Ice.

Nov. 26, 2015. This week started off with the very important and always somewhat nerve-racking step of moving Theo (our cryostat) to the gondola from its ground station cart. We are well practiced at this maneuver, but you always have to be on your A game when transporting a cryogenic vessel that’s under vacuum. Happily, this went off without a hitch on Sunday!


Theo mounted on the gondola, along with a bunch of people in hard hats.

After that long day on Sunday, we were told to take Monday off in preparation for the very busy next month that spans from the first helium fill until launch. We took full advantage of the day, starting with a trip to the Observation Tube.

The Obs Tube is a tube situated in the sea ice just down the hill from town. It fits one person, and takes you via ladder down a few meters to a compartment with windows below the ice. I don’t have any more adjectives to describe these sort of incredible experiences I’m having down here! The sea is brimming with life, despite the cold. Tiny white fishes are everywhere moving in slow motion. Little transparent white skeletal looking creatures and tiny jellyfish-looking things make you double take as you realize they are alive. And the coolest part- the sounds of the whales or seals. We imitate them to each other and it sounds like we are making lame sci fi laser gun sounds effects: “Pew pew!” But that’s exactly what it sounds like.

Obs tube

Evaluating the Obs tube

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After that, Ed and I hit the gym to do some climbing. There are three gyms here- the weights gym, the gerbil gym, and the big gym. Here is a picture of the big gym.

The Gym

The Gym

The next day, we took the dive and put liquid helium into the main tank. Cooling something down to near absolute zero causes a lot of boil-off and high pressures in the tank, so we do it slowly and keep people around for the 72 hours it takes for everything to equilibrate, just to make sure Theo is happy. So far, so good! Tomorrow, we should have superfluid, and within a day or two after that, a fully functioning instrument!

Back to work the next morning!

Back to work the next morning!

SPIDER has a grand tradition of terrible weather (including a couple of hurricanes) interrupting important operations). On the day of our first helium fill, we saw our first “Condition 2″ weather, which thankfully wasn’t enough to keep us from our work. You can see from the bent flag here how windy it was though.

SPIDER has a grand tradition of terrible weather (including a couple of hurricanes) interrupting important operations). On the day of our first helium fill, we saw our first “Condition 2″ weather, which thankfully wasn’t enough to keep us from our work. You can see from the bent flag here how windy it was though.

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Jeff Filippini

Jeff Filippini

SPIDER is designed to measure the polarization of the cosmic microwave background (CMB), the afterglow of the Big Bang. With SPIDER closed up and cooling toward its operating temperature, it’s a good time for a quick look at the telescopes that make this measurement possible.

SPIDER is designed from the ground up to target the signature of primordial gravitational waves in the CMB’s polarization. These gravitational waves should produce ripples in the sky’s polarization that are incredibly faint: equivalent to variations of the sky’s temperature by less than 100 billionths of a degree (100 nanoKelvin). Though dim, these ripples should also be relatively large: several times of the size of the full moon. This means that it’s perfectly fine to make a fairly blurry map of the sky, as long as our instrument is enormously sensitive and immune to false polarization signals. SPIDER is designed with exactly this in mind, and when it flies it should be the most instantaneously-sensitive CMB polarimeter ever deployed.

A single SPIDER telescope assembled on the bench

A single SPIDER telescope assembled on the bench

SPIDER’s eyes are six refracting telescopes, each about a foot in diameter and four feet long. These telescopes were designed, built, and tested by the SPIDER receiver team at the California Institute of Technology (Caltech). Each telescope underwent a program of careful electrical and optical testing at Caltech before being integrated with the flight payload. A pair of lenses in each telescope (the objective and the eyepiece) focus light from the sky onto a focal plane populated with superconducting detectors. The lenses are shaped slabs of white polyethylene plastic, opaque to visible light but transparent to microwaves. Each lens is coated with a layer of porous Teflon to reduce reflections within the optical system. This basic telescope design was developed for the BICEP instrument, which observed at the South Pole from 2006-2008, and later for the BICEP2 and Keck Array instruments.

Protecting our sensitive detectors from stray light was a major concern in SPIDER’s design. More stray light means more noise, which means lower instrument sensitivity. This is the main reason why we lift SPIDER on a balloon: to raise it above the bulk of the glow from the earth’s atmosphere, so that the CMB is the dominant light falling on it at the relevant frequencies. The entire telescope is cooled to liquid helium temperatures (4 degrees above absolute zero, or -452 Fahrenheit) in order to reduce the thermal glow from the telescope itself. Most of the surfaces visible to the detectors are even colder to further reduce this internal radiation: 2 degrees above absolute zero, or -454 Fahrenheit. A stack of reflective and absorptive filters protects the delicate detectors from stray light from the outside world, particularly infrared light that might warm them too much.

The front (sky) side of a SPIDER focal plane, showing the four silicon tiles

The front (sky) side of a SPIDER focal plane, showing the four silicon tiles

The heart of a SPIDER telescope is its detectors, developed jointly by Caltech and NASA’s Jet Propulsion Laboratory (JPL). These detectors are complete millimeter-wave polarimeters, photolithographically patterned onto standard silicon wafers, with no need for external feed horns or band-defining filters. Power absorbed by an on-chip planar antenna is filtered to select the desired frequencies and then dissipated to heat a tiny suspended island of silicon nitride. Changes in the incident radiation cause the island to rise or fall in temperature, which is detected by a sensitive superconducting thermometer. Each polarimeter pixel consists of two such detectors with interleaved antennas, one for each perpendicular polarization direction. Four silicon tiles full of such pixels populate the focal plane in each telescope. The detectors must be kept extremely cold in order to operate: the entire focal plane is cooled to 0.3 degrees above absolute zero by a helium-3 sorption refrigerator.

Photograph of a SPIDER detector island. The central island (0.3mm long) is suspended over a pit in the surrounding silicon wafer by thin legs.

Photograph of a SPIDER detector island. The central island (0.3mm long) is suspended over a pit in the surrounding silicon wafer by thin legs.

Among its six telescopes SPIDER has 2300 sensor channels: 864 sensitive to 100 GHz radiation, 1536 sensitive to 150 GHz radiation. Those detectors are currently dormant, awaiting temperatures low enough to operate. If things go according to plan, we should be cold enough to wake them up next week.

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Photos from the past

Jon Gudmundsson, PhD CandidateWorking on SPIDER for the last 6 years has allowed for some nice photo opportunities. Here, I look back at some of the more memorable photos from the the years past.


This photo shows the flight cryostat (the part that keeps the six telescopes cold) in its most fragile state, completely naked. A swiss-cheese-like structure with six, one meter long, peripheral inserts designed to house our telescopes. The cryostat was built while the telescopes were still in development phase. It arrived in Princeton early in 2010. The first couple of years, while the telescopes were being built, we were learning how to work with this system, one of the largest cryostats of its kind.


As part of flight qualification, in 2012 we inserted the entire cryostat into a gigantic vacuum chamber operated by the NASA Plum Brook facility. This chamber, normally used to test the performance of rocket engines, made us feel quite small. This image shows the cryostat as it is being lowered down into the chamber, a somewhat nerve wrecking experience.

Our working environment has historically been rather poorly lit, especially if you’re hoping for good photo opportunities. There are exceptions, however. This photo shows a former SPIDER postdoc, Cynthia Chiang, performing a routine task: setting up a nitrogen purge on our main cryogenic vessel in preparation for cooldown. The warm tones from our halogen floodlight really sets the mood.

Speaking of warm tones. Again, with the help of our halogen floodlight, we see the strong reflections in the magnetic shields that are located inside each telescope insert. These concentric dual layer structures are designed to siphon any magnetic fields that would otherwise interfere with the sensitive detectors at the heart of our telescopes.

Here we see Anne Gambrel (Princeton) and Sean Bryan (then at CWRU) doing science! Anne, with extreme care, is building a telescope on the bench next to the flight cryostat, while Sean is configuring the SPIDER half-wave plates that we use to modulate the polarization of incoming light.

This is the view of the top of the flight cryostat before the telescopes are installed. The half-assembled aluminum shield represents the first wave of resistance against thermal radiation that would otherwise paralyze the cryogenic performance of our system. To clarify: The telescopes need to be cooled to a fraction of degree above absolute zero. To achieve this goal, we use liquid cryogens (helium). That helium will boil off over time, and since we have a limited amount for flight, we need to do a good job at isolating the tank from the outside elements.

In 2013, we shipped all of our equipment to Palestine, Texas, where CSBF, the NASA facility that oversees long-duration ballooning flights, operates. We spent the entire summer building and testing the instrument in preparation for a 2013 Antarctic flight. The government furlough in 2013 then delayed us by a year. Occasionally, we would had beautiful night skies like the one shown here. Here, Princeton Postdoc Zigmund Kermish is seen looking up at the sky, while the Principal Investigator, Prof. William Jones, attends to the back of the flight cryostat.

During this testing phase in Palestine, we would occasionally drag the payload out onto the tarmac. From there, we could test our solar panels and calibrate our telescopes using bright objects stationed at moderate distances. This is the view of the payload from the top of our high bay. The negative space makes this photo an ideal candidate for slide #1 on our Power Point presentations.

Now, after about six years of development, the SPIDER payload is finally getting ready to deploy from Antarctica. This photo shows the back of our six telescopes after they have been inserted into our cryostat, here at LDB camp in Antarctica. We have now closed up the flight cryostat for the last time. Pretty soon we’ll have a fully integrated payload. I’m sure this season will bring lots of great photo opportunities.

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