ARC 3.5m | Instrument Summary

There are six main instruments currently in operation at the ARC 3.5m telescope:

• ARCES (Echelle): the ARC Echelle spectrograph, a high resolution (R~31,500) echelle spectrograph that observes the entire wavelength range from 3200 Å to 10000Å in a single image on a 2048x2048 CCD. This instrument is permanently mounted at the NA1 port.
• ARCTIC: the ARC Telescope Imaging Camera, a direct imager with a field of view of 7.5 arcminutes. A variety of filters are available to be placed in a 6-slot filter wheel.
• DIS: the Dual Imaging Spectrograph, a medium resolution (R~1000-7000), two channel, long-slit spectrograph with a dichroic that splits the spectrum at ~5350 Angstroms. Two grating pairs are available at any one time with a motorized turret, allowing for either lower dispersion spectroscopy covering the entire wavelength range from the atmospheric cutoff to the CCD cutoff, or higher dispersion spectroscopy covering a fraction of the observable range. A third position allows for direct imaging.
• NICFPS: the Near-Infrared Camera and Fabry-Perot Spectrometer, an infrared instrument that provides NIR imaging capability of a 4.5 arcmin square FOV on a 1024x1024 Rockwell Hawaii 1-RG HgCdTe detector. The instrument has a large complement of broad and narrow band filters, and includes a cold Lyot stop to reduce thermal background. The instrument also has the capability to use a cryogenic etalon to work as a Fabry-Perot spectrograph at R~10,000; this capability is still (2007) in the process of being implemented.
• AGILE: a high speed imaging camera that uses a commerical frame transfer 1024x1024 CCD to image a 2.5 arcmin square FOV. Images can be taken continuously, with no dead time, down to an exposure time of 0.5s.
• TRIPLESPEC: a medium resolution IR spectrograph that will deliver spectroscopy across the JHK windows in a single exposure at R~2700.

ARCES is permanently mounted at the NA1 (Nasmyth) port and Agile is mounted at the TR2 port, while the other four instruments can be mounted at the NA2 port. Switching between ports using the tertiary mirror can be accomplished in less than 5 minutes. Switching instruments at the NA2 port can be done within 15-20 minutes, allowing for the capability to do rapid instrument changes for target of opportunity observations, or to adjust to different observing conditions.

In addition to the facility instruments, several visiting or non-facility instruments have been used at the 3.5m, and some of these are available to the ARC observing community by contacting the instrument PIs:

• NAIC : NMSU Acousto-optic Imaging Camera, a visiting imager that provides a tunable filter for adjustable very narrow band imaging.
• APOLLO: the Apache Point Observatory Lunar Laser-Ranging Operation, an instrument that is attempting to map the orbit of the Moon by distance measurements at an accuracy of ~1mm, using a laser that is beamed up through the telescope and reflects off retroreflectors previously left on the Moon.
• Goddard Integral Field Spectograph (GIFS): (decommissioned March 2016) a visible Imager and Integral Field Spectograph (IFS). This used to be known as the Goddard Fabry-Perot (GFP). The IFS has an R=1475 for the green grism and R=1823 for the red grism. Field of views for the IFS are 7x7 or 14x14 square arc-seconds.
• CORMASS: (decommissioned March 2008) a low resolution (R~300) IR spectrograph providing simultaneous coverage of the IJHK bands

Finally, several engineering instruments are also used:

• FASTCAM: a high speed (100 Hz) imaging camera used to diagnose image motion issue
• Puntino: a Shack-Hartmann sensor, built by SpotOptics, used for optical alignment of the telescope