Cold Detectors and Compatibility

12/19/2022

(Seals and penguins at the bottom of the post)

We started the process of cooling Lloro down in mid-November with liquid nitrogen, LN2 has a boiling point of 77 Kelvin (~-320 F). We waited a few weeks with LN2 in the cryostat, for enough of the liquid helium dewars to arrive from Australia to switch over to helium. LHe has a boiling point of 4 Kelvin (-454 F), four degrees above absolute zero, taking the dectors closer to the operating temperature at 0.3 Kelvin.

The CMB polarization anisotropies are a very faint and cold signal on the sky, so our detectors and instrument must also be very cold. Otherwise the thermal glow of the telescope would saturate our own detectors and overshadow the CMB signal we are trying to detect.

Our liquid helium arrived at the end of November and we started the slow process of getting the cryostat down to base temperatures on 11/29, and had cold detectors by Saturday the 3rd. Then began the rush to compatibility and being flight ready ASAP.

So the last week or so I have been very busy getting the detectors tuned up and in their operating state, taking some calibration measurements and then analyzing the data, and spending lots of time looking at the flight code, and learning how we will monitor the detector performance during flight with the other detector experts.

Other people on the team are getting the whole payload ready to go. In the last few weeks we integrated Lloro with the Gondola, so she is a lot taller now. The sunshield and solar panels were put together and installed this week. Everything is getting thermal treatment that will be in the sun, to keep the temperatures down. At float altitude there isn't any air to help convect heat away, so bare metal is bad. We paint exposed bits white, or cover them with aluminized mylar. The aluminum layer reflects, and the mylar plastic is emissive (unlike aluminum) and lets heat radiate away.

We have Compatibility tests today, where we will check all our systems with NASA's, and a launch hopefully early morning tomorrow. The weather looks potentially promising the early AM. We'll see. Lots of things to do in the mean time. It is getting warmer every day, last week lots of high 20s many days above freezing. I walked around in a T-shirt outside last Monday, a welcome cool-down break when the high-bay gets to be above 80 inside.

The launch pad is getting slushy, but dragging a bull dozer on a magic carpet made out of high-density polyethylene with another bull dozer seems to be working to tamp it down.

When we launch there will be a live video feed somewhere on this website: https://www.csbf.nasa.gov/antarctica/ice.htm probably the "Operations Video" link on the left hand side. Our twitter @SPIDER_CMB will have the most up to date information.

Team photo with the cryostat's first sunbath on the deck.

A beautiful sight at LDB, lots of liquid helium

Last checks of gondola electronics before adding Lloro

Bill unwrapping the helium transfer lines

The Boss, the launch vehicle, doing a workout getting ready for launches.

Spied a Corwin over the top of the cryostat

Simon carefully wrapping the sun shield in aluminized mylar

Sho helping install the sunshield on the gondola

Jared, Suren, and Sho admiring their handiwork. Notice the really handy trap door for accessing the computers

Its not a ballooning campaign if you don't "destroy a circuit board in a controlled and deliberate manner"

SPIDER on the deck for TDRSS (one of the sattelite antennas) testing.

SPIDER with her shiny mylar pants on, and a solar panel array!

Some other photos from late November!

The night after the Thanksgiving celebration it snowed and got really windy. It was condition 1 out on the ice shelf overnight, and we arrived out at LDB on monday to see some awesome snow drifting.