6.1.3 Filter Suite
The core of the FLITECAM filter suite is a set of standard Barr bandpass filters used for imaging at J, H, K, L, & M, which are all located in filter wheel #1. In addition, filter wheel #2 holds a selection of specialty, narrow-band imaging filters, including Paschen α, Paschen α continuum, an ice filter centered on the 3.07 μm H2O ice feature, a polycyclic aromatic hydrocarbon (PAH) filter centered on the prominent 3.3 μm feature, Lnarrow, and Mnarrow. Finally, there are a number of order sorting filters (OSFs) for use with the grisms, including J and H (both dual purpose), Kwide, Klong, and ''L+M''. Additional details of the OSFs are given in Section 6.1.5.
As the bulk of the instrument commissioning was performed in the combined FLITECAM/HIPO (FLIPO) mode, some of the FLITECAM only observation modes lack detailed performance characterics. This is due to the lack of circulation of stratospheric air down the Naysmyth tube which keeps the FLIPO foreoptics at cabin temperature, greatly increasing the observed background.
In the combined FLITECAM/HIPO configuration, imaging observations past 3 microns are required to use increasingly small subarrays; spectroscopic observations past 4 microns are not possible at all. In the FLITECAM-solo configuration, however, full-frame imaging observations are possible out to 4 microns, and the full suite of FLITECAM grisms are available.
The central wavelengths and band widths of the available imaging filters are provided in Table 6-1. This table also includes the sensitivity values (Minimum Detectable Continuum Flux; MDCF) discussed in Section 6.1.4. Filters that will only be available on a shared risk basis during Cycle 5 are indicated. Figure 6-3 displays the transmission profiles (normalized to their peak transmission) for the imaging filters over-plotted on an ATRAN model of the atmospheric transmission. The filter transmission curves are available and linked in the last column of Table 6.1, below.
Table 6-1: FLITECAM Filter Characteristics
| Desig- nation |
Pass- band |
λeff (μm) |
Peak Trans. (%) |
5% Band- widtha (μm) |
R (λ/Δλ) |
MDCFb (μJy) |
MDCFc (μJy) |
Profiles | |
|---|---|---|---|---|---|---|---|---|---|
| Standard Filters | |||||||||
| FLT_J | J | 1.239 | 93.7 | 0.293 | 22.3 | 25.7 | 27.4 | PNG DAT | |
| FLT_H | H | 1.631 | 95.3 | 0.305 | 17 | 33.5 | 35.7 | PNG DAT | |
| FLT_K | K | 2.104 | 95.4 | 0.395 | 16.8 | 38.7 | 57.5 | PNG DAT | |
| FLT_Lprime | L′ | 3.855 | 93.5 | 0.7 | 15.7 | - | - | PNG DAT | |
| FLT_L | Ld | 3.53 | 94.1 | 0.65 | 15.7 | 440 | - | PNG DAT | |
| FLT_M | Md | 4.838 | 91.8 | 0.645 | 10.8 | 2720 | - | PNG DAT | |
| Specialty Filters | |||||||||
| FLT_Pa | Pa α | 1.874 | 84.2 | 0.033 | 1.2 | 179 | 195 | PNG DAT | |
| FLT_Pa_cont | Pa α Cont. | 1.9 | 88.3 | 0.033 | 1.2 | 178 | 195 | PNG DAT | |
| FLT_ICE_308 | Iced | 3.049 | 88.1 | 0.191 | 5.2 | 504 | 1130 | PNG DAT | |
| FLT_PAH_329 | PAHd | 3.302 | 91.4 | 0.115 | 2.7 | 1070 | 2260 | PNG DAT | |
| FLT_NbL | Lnarrowd | 3.602 | 90.5 | 0.231 | 5.1 | 1010 | 2110 | PNG DAT | |
| FLT_NbM | Mnarrowd | 4.804 | 89.5 | 0.19 | 3.1 | 5430 | - | PNG DAT | |
| Order Sorting Filterse | |||||||||
| Hwide | Hwide | 1.794 | 97.1 | 0.587 | 29.1 | - | - | PNG DAT | |
| Kwide | Kwide | 2.299 | 96 | 0.882 | 35.3 | - | - | PNG DAT | |
| Klong | Klong | 2.45 | 95.5 | 0.55 | 19.3 | - | - | PNG DAT | |
| L+M | L+M | 4.11 | 92.5 | 2.715 | 64.2 | - | - | PNG DAT | |
a Bandwidth for transmission level is >5%
b See Section 6.1.4
c Empirically measured MDCF values when FLITECAM is co-mounted with HIPO in the FLIPO configuration.
d Will be offered as Shared Risk during Cycle 5
e Will not be available for imaging
Figure 6-3: Plotted here are the FLITECAM filter transmission curves overlayed on an ATRAN model of the atmospheric transmission across the FLITECAM bandpass assuming a zenith angle of 45 degrees and 7 μm of precipitable water vapor. The transmission profiles of the standard filters are shown in red, specialty filters are shown in blue, and OSFs in gold. The OSF transmission profiles have been scaled by 50% for clarity.
