MIRLIN Filter SelectionMIRLIN provides wavelength coverage from 5-26 µm by having a large selection of filters and a CVF mounted in two filter wheels and are thus changeable in real-time. The filter set includes the M, N, Q, Q-short, and Q-long filters, the OCLI 6-filter 10 µm silicate set, a 7-filter narrow-band 20 µm set, and a 7-14 µm, 2% resolution CVF; however, the available filter slots are limited, so we have gradually whittled the selection down to these 13 filters (plus the CVF):
Note that the broadband N filter cannot be used in the full frame mode at Keck and the IRTF because we cannot read out the array fast enough to avoid saturating without significantly reducing the bias voltage. An ability to read out half frames (64 x 128 pixels) is now available and has been used very successfully at the IRTF. The following filters are also lying about in a box in my lab, and will be swapped in only if you offer a sufficiently large reward (e.g. a new array or dewar):
The reason these filters were deselected is that antireflection coatings kill the K and M sensitivity (less than 1% transmission, so there is almost literally no sensitivity); no one ever used the Q-long filter due to it's breadth and the general trashiness of the atmosphere over this band; and Q4 was dropped because it was deemed the least useful 20 µm filter for Jupiter observations. In general, the most used filters are N at Palomar, the N0-N5 silicate filters everywhere, and the Q-short, Q3, and Q5 filters when the weather on Mauna Kea permits their use.
For questions about this page please contact: Dr. Michael Ressler (Michael.E.Ressler@jpl.nasa.gov) |