Background Research AntiShock Material material selection for launching

Background Research

Anti-Shock Material • material selection for launching of telescope; must be soft, able to absorb vibration, fit within the appropriate temperature range and durable under radiation • use steel wrapped in PTFE (teflon) and coated with Halpern Anti-Radiation Paint (HARP) • HARP is paint coated with tiny conductive flakes of copper and aluminum Telescope Teflon Steel Image: telescope nailed down into steel wrapped with Teflon

Material for a Filter • Mars is exposed to high levels of solar radiation • telescope to be used in conjunction with a charged coupled device (CCD) • CCD’s maximum allowable light intensity is: 37 n. J x 1/(0. 01)2 m 2 x 1 frames/30 s = 0. 0111 W/m 2 but the solar intensity on Mars is 590 W/m 2 37 n. J/cm 2 - maximum energy/cm 2 for the DALSA 2 M-30 1/(0. 01)2 m 2 - unit conversion from cm 2 to m 2 1 frames/30 s - CCD’s frame rate

• solar radiation will cause electron well saturation (blooming) or permanent damage to the CCD • each individual pixel is a quantum electron well • as wells fill up (saturate), the probability of trapping an electron greatly decreases and electrons spread onto adjacent pixels (blooming) instead of filling into the correct pixel Image: white streaks (saturation trails) produced due to spillovers to adjacent wells

• a filter is designed to attenuate visible light wavelengths and eliminate all infrared and ultraviolet light • CCD is most effective around =500 nm • Eliminate below 300 nm and above 700 nm 100 Transmission % Transmission curve: This type of transmission can usually be obtained by a combination of Schott glasses 61% Transmission 50 250 500 Wavelength (nm) 750

• to find the amount of attenuation needed, Fourier optics is used Fourier far away light source optics will be discussed in more detail later Instead of a perfect point, a blurspot is formed due to diffraction effects • on the pixel array, the image of the sun appears with an intensity of I kasin I(0) is the maximum intensity and is directly related to the parameters of the first lens in the telescope J 1 is the Bessel function and its value may be found in mathematic tables kasin is the radius from the center point of a blurspot

• to prevent electron well saturation, only 0. 01 or 1% of the solar light coming in can be transmitted • photosensitive glass with gold-palladium particles used 100 Transmission % 40% Transmission 50 250 500 Transmission curve: Ag. Pd particles deposits in glass 750 Wavelength (nm) • with the above filter in conjunction with the IR and UV filter, only 1% of the light will be transmitted

Geometric Optics • ideal optics - every point or object is perfectly imaged • for thin lenses: nm is the index of refraction of the surrounding medium nl is the index of refraction of the lens s 0 is the distance from the object to the lens si is the distance from the lens to the image f is the focal length of the lens • magnification of lens: Object So Si Image

• ray tracing lens principal plane parallel focal ray: refracted through focus F ray: goes through focus F and then refracted parallel to the principal plane central ray: passes through center of lens

Fourier Optics • when plane waves of light hit a lens, only a fraction of the light is collected because no lens or object can be infinitely large • the diffraction pattern formed by the lens can be found by taking the Fourier transform of the aperture and convoluting with the Fourier transform of the original image (object) Distant point source such as a star (delta function) Image of point source produced by a circular lens is often called an Airy disk: top view Airy disk: side view

Aberrations • departures from the idealized conditions of geometric optics • chromatic aberrations Result of a lens focusing different wavelengths of light at different points Distortion in image colouring occurs Possible correction method

• monochromatic aberrations include coma, spherical aberration and astigmatism - focus points do not all coincide on the principal axis coma • pincushion and barrel distortions - caused by imperfections in the lens original pincushion barrel

Preliminary Design of Telescope • the minimum allowable diameter of the lens is first calculated • diameter is limited by angular resolution and collecting power (in radians) - angular resolution D - diameter with a required angular resolution of 22. 5 arcseconds, D = 1. 22(500 nm)/(22. 5/3600 x /180) = 0. 56 cm collecting power of lens 8. 644 x 102 W/m 2 - the minimum power of a star with the Signal-to-Noise Ratio >= 10, D >= 0. 3648 cm

• considered thin lenses when lens thickness<<focal length and the diameter of lens<<2 x radius of curvature of lens 3 cm radius of curvature example: 3 cm 3 cm radius of curvature 1 cm << 6 cm 1 cm lens diameter 4. 5 cm lens diameter plano-convex lens negligible thickness not negligible thickness

Design: f = 1 cm f = 3 cm parallel rays: image at infinity 1. 247 cm CCD 7. 06 cm 3 cm both lens diameter =1 cm blurspot size after first lens = 2. 44 /D = 3. 66 x 10 -6 m Blurspot - central part of Airy disk desired 7. 4 m blurspot size (to span 4 pixels) = 2 x 7. 4 m = 14. 8 x 10 -6 m magnification factor needed = 4. 044