After shipping, unpacking, and verifying that everything still works, the last step was for Manny and Richard to cool Clio2 down. Then they took some pictures.
Since it works in the IR, basically detecting the heat of planets and brown dwarfs, Clio2 is kept very cold. This is because a blackbody at room-temperature emits most of its energy at a wavelength of about 10 μm, according to Wien’s law. A lot of flux from the tail of the distribution is also emitted at near-IR wavelengths of 1–5 μm. Therefore, for IR astronomy, it is important to keep the telescope and the instrument cold, to avoid this excess thermal flux, which shows up as noise in our images (you’ll hear us call it “sky” or “background”).
To make this work, Clio is contained in a dewar, which is a kind of vacuum flask (a.k.a. Thermos) — an insulated canister that keeps cryogenic material at very cold temperatures. Clio2 has a nested-dewar design with an outer and an inner vessel. The cryogen we use is liquid nitrogen, which has a boiling point of 77 K stp. We also lower the pressure in the inner dewar, using a vacuum pump, in order to solidify the nitrogen (55 K). A blackbody of 77 K emits most of its radiation at ~38 μm, and a blackbody of 55 K emits most of its radiation at ~53 μm. These wavelengths are well beyond what we care about when hunting planets.
The invasion of LCO has begun. A scouting party consisting of Manny Montoya and Richard Sosa arrived this weekend and began unpacking the Clio2 infrared camera. Here is their report:
Day 1: “Clio was unpacked yesterday morning and we confirmed that nothing was damaged in shipping. Clio was put on the vacuum pump and we confirmed that we had not lost vacuum. The electronics rack and other stuff was unpacked and accounted for. The electronics rack cabling was tied down a little more securely since this was not possible before it left Tucson, and we also confirmed that nothing had broken during shipping. One thing that did get a little tweaked was the monitor and keyboard support to rack were bent. We straightened them out and put nuts behind it to make it more secure. The rack was then plugged into Clio and the computer, temp. controller, motor control were all tested, checking both the physical conection and through the runclio command on the gui. We then plugged into the network, it was not working so Emilio helped us with the vlan connection.”
Day2: “This morning we took the ring up to the telescope and confirmed that it fit on the MagAO NAS. We also checked the flower box to window measurements, we still have to check these with Clio to confirm there are no collision points, but the ring did fit. After the ring was confirmed to fit, we took it back down and put Clio2 and its cart together. This afternoon we are moving everthing into the clean room to prepare for cooling of Clio2 tommorow.”
While the NAS was mounted on the telescope we took a quick set of readnoise measurements with the CCD39. Here are the results. The only major caveat is that the telescope was not tracking, so we didn’t test whether the drives have any impact. Otherwise, this is the most realistic set of RON measurements we have taken to date. We are very happy with the results, especially the 156kHz 3.8 electrons. This number essentially sets the limit to how faint our guide star can be, so keeping it low is important.
Pixel Rate (kHz)
Frame Rate (fps)
Note: these are determined using the actual gains from Scimeasure, rather than assuming 0.5. This can cause as much as an 8% difference.