b'Automotive & Transportation | Engineer InnovationFigure 1: Solar filament as captured by NASAs Solar Dynamics Observatory (SDO) Credit: NASA/SDO/AIA/GSFCspace telescope, it will be relatively easy to upgrade the technology of the DKIST throughout its lifetime.A solar telescope-specific problem isthe heat generated by the tightly-focused sunlight. Unlike most large ground-based telescopes, which are used at nighttime to capture a small number of photons from distant astronomical bodies, the DKIST will spend its working life pointed directly at the sun, absorbing large quantities of focused light andheat energy.A heat stop is an integral part of the design of solar telescopes, and represents one of its larger engineering challenges. It performs the role of whatFigure 2: Located at the prime focus, the heat stop limits the field of vision of the telescope and is called a field stop in a conventionalabsorbs large amounts of solar energy, preventing it from reaching subsequent optics.telescope, limiting the field of vision to the area with minimal distortion.approximately 1,700 W at peak operating Located at the prime focus, the heat stopload (see side box for a discussion of prevents unwanted solar disc light fromporous metal heat exchangers).heating and scattering on subsequent optics. In a solar telescope such as theThe heat stop must not only be able to DKIST, in addition to blocking light, thesurvive this heat load (without cooling, heat stop must also dissipate hugethe heat stop reflector would last only amounts of thermal energy. about 30 seconds before catastrophic failure), but also must remain cool For the upcoming DKIST, the heat loadisenough not to induce any additional 2.5 MW/m2, reducing the heat loadonturbulence inside the telescopes dome.subsequent optics from an enormous 12 kW to a minuscule 300 W (a reductionOne of the obstacles of ground-based factor of 40). Designed by Thermacore,astronomical observatories is a the heat stop assembly is actively cooledphenomenon known as self-induced by an internal system of porous metalseeing." It consists of the degradation of heat exchangers that dissipateimage quality, mostly resulting in an 47'