Toward miniaturizing cross-dispersed echelle spectrographs: a first approach design of a white pupil cross-dispersed echelle spectrograph with a Cassegrain collimator

Cross-dispersed echelle spectrographs (CDESs) are a fundamental tool for modern astronomy. Their spectral power relies on the echelle pupil size and collimator focal length. Due to this, seeing-limited ground-based observatories often require large instrument sizes to achieve high spectral resolutions. With the advent of large-aperture telescopes and the unrelenting demand for high resolution, the prevailing trajectory of these instruments leans toward escalating in both size and complexity. However, it is important to explore miniaturization strategies for CDESs, which are particularly valuable for space-based instruments where size, weight, and power are crucial. Miniaturization also offers benefits for ground-based instruments, enabling the use of compact, high-resolution CDES systems in lab setups for academic use and as cost-effective solutions for small to medium telescopes in professional observatories. Although there exist miniaturization strategies and designs such as the double pass with a three-mirror anastigmat, they can be challenging to implement due to their sensitivity to alignment. We present a first approach design of a CDES using a Cassegrain collimator. This approach effectively has a reduction in instrument footprint while achieving high spectral power, when compared with the three-fold design. We also performed a sensitivity analysis for the alignment of this design and showed that at a smaller scale, the design does not offer added complexity when compared with the three-fold design.