Beyond the Veil, but not Beyond Reach

When I awake each afternoon during an observing mission at the Cerro Tolo Inter-American Observatory (CTIO), I have one priority. Before I eat, before I check e-mail, before I even stretch, I step out the door and look to the west: are our skies clear? Clouds can cast a shroud over a night’s observing program for the Dark Energy Survey (DES), which is now in full swing, each night gathering a terabyte of clues to dark energy. If our view is blocked by clouds, if we’re not taking data and peering into the deep black, we’re missing precious opportunities to observe space-time’s expansion.

To mitigate this, the Dark Energy Survey has developed another tool to pierce the veil of Earth’s atmosphere: the Radiometric All Sky Infrared Camera, or RASICAM.

The video above shows RASICAM closed during the day and then open after sun-down. RASICAM sees the entire sky in the infrared wavelengths, where our eyes are blind, but the clouds show up clearly. DES scientists and engineers at the Stanford Linear Accelerator Center (SLAC) National Laboratory designed and constructed this all-seeing eye on the infrared sky, and it’s been operational at CTIO since 2011 (http://today.slac.stanford.edu/feature/2010/rasicam.asp). In future posts, we’ll look at the sky from RASICAM’s point of view.

RASICAM is critical to DES operations. We use this camera to help inform us about how many clouds are in the sky, as well as where they are. We can then adjust our observing strategy and better analyze the image data. The instrument is brought to us by Rafe Schindler, Peter Lewis and Howard Rogers. Data analyses and maintenance are performed regularly by Kevin Reil, Dave Burke, Peter Lewis and Zhang Zhang.

Occasionally, clouds may appear or rain may fall, but dark energy cannot hide from us.

Det. B. Nord