Performance comparison of two Wolter type II telescopes in the far ultraviolet

Area of Science:

• Solar physics
• Astronomy
• Optical engineering

Background:

• Selection of optimal telescope optics is critical for high-resolution solar observation in the extreme-UV spectrum.
• Conventional vs. advanced polishing techniques impact telescope performance in specific wavelengths.

Purpose of the Study:

• To evaluate and compare the image quality and scatter characteristics of two Wolter type II solar rocket telescopes: SERTS-A and SERTS-C.
• To determine the most suitable telescope for an extreme-UV flight instrument based on experimental results.

Main Methods:

• Laboratory experiments were conducted to measure image quality (Full Width at Half Maximum - FWHM) and scatter in far-UV light (124 nm).
• Comparative analysis of optical performance metrics between the conventionally polished SERTS-A and the computer-controlled polished SERTS-C.

Main Results:

• The SERTS-C telescope achieved a significantly sharper image with a 0.67-arcsec FWHM compared to SERTS-A's 1.25-arcsec FWHM at 124 nm.
• SERTS-C demonstrated twice the peak irradiance and an order of magnitude lower near-angle scatter than SERTS-A.
• In-flight performance data corroborated the laboratory findings for both telescopes.

Conclusions:

• The computer-controlled polishing of SERTS-C results in superior far-UV image quality and reduced scatter.
• SERTS-C is the recommended telescope for future extreme-UV solar flight instruments due to its enhanced optical performance.