Near-infrared Imaging Spectropolarimeter For The Nst

The NST Near-Infrared Imaging Spectropolarimeter is one of the first imaging solar spectro-polarimeters working in the near infrared (NIR). It has been installed and commissioned in the Coude Lab of the 1.6-meter NST at Big Bear Solar Observatory (BBSO). This innovative system, which includes a 2.5 nm interference filter, a unique 0.25 nm birefringent Lyot filter, and a Fabry-Perot etalon, is capable of providing a bandpass as low as 0.01 nm over a field-of-view (FOV) of 50" in a telecentric configuration. An NIR waveplate rotates ahead of M3 in the NST as the polarimeter modulator, and ahead of it a calibration unit is located to reduce polarization cross-talk induced by subsequent oblique mirrors. Dual-beam differential polarimetry is employed to minimize seeing-induced spurious polarization. Based on the unique advantages in IR window, the very capable NST with adaptive optics, it will provide unprecedented solar spectro-polarimetry with high Zeeman sensitivity (10^-3I_c), high spatial resolution (0.2"), and high cadence (15s). In this presentation, we discuss the design, fabrication, and calibration, as well as showing the results of the first light observations.