A Compact, Ultra-high-resolution Virtually Imaged Phased Array Spectrograph for Solar Spectroscopic Observations: Astrocomb Characterization and First Light

We present a compact, high-spectral-resolution prototype spectrograph based on a Virtually Imaged Phased Array (VIPA), which is designed for solar spectral observations. This fiber-fed instrument has a size of only 53 × 20 × 18 cm 3 . Wavelength calibration using an astrocomb ( f rep = 25 GHz) established an operational bandpass of 592.76–657.07 nm and revealed an asymmetric instrumental profile. A Fano–Lorentz product function provides a significantly better fit to this profile than a Gaussian. The measured spectral resolution ranges between 290,000 and 340,000 across the band. Initial on-sky validation at the New Vacuum Solar Telescope (Yunnan Observatories) successfully demonstrated the prototype’s capabilities: clear detection of solar 5 minute oscillations (±300 m s −1 ) in the Fe I 6280.57 Å line, resolution of magnetic broadening in sunspots using the Fe i 6173.34 Å line, and the first ground-based definitive identification of the faint Si i 6560.57 Å line within the H α band. These results validate the VIPA as a promising platform for high spectral resolution solar spectroscopy. Its compact design and performance directly support future applications in multiobject solar studies, high spectral resolution observations for time-domain astronomy, including exoplanet detection, and potential spaceborne instrumentation.