Background Research

1. Background Research

2. 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 Image: telescope nailed down into steel wrapped with Teflon Teflon Steel

3. 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: 37nJx 1/(0.01)2 m2 x 1 frames/30s = 0.0111W/m2 but the solar intensity on Mars is 590W/m2 37nJ/cm2 - maximum energy/cm2 for the DALSA 2M-30 1/(0.01)2 m2 - unit conversion from cm2 to m2 1 frames/30s- CCD’s frame rate

4. • 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

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

6. • to find the amount of attenuation needed, Fourier optics is used Fourier optics will be discussed in more detail later Instead of a perfect point, a blurspot is formed due to diffraction effects far away light source • 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 J1is the Bessel function and its value may be found in mathematic tables kasinis the radius from the center point of a blurspot

7. • 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 % Transmission curve: AgPd particles deposits in glass 40% Transmission 50 250 500 750 Wavelength (nm) • with the above filter in conjunction with the IR and UV filter, only 1% of the light will be transmitted

8. Geometric Optics • ideal optics - every point or object is perfectly imaged • for thin lenses: nmis the index of refraction of the surrounding medium nlis the index of refraction of the lens s0is the distance from the object to the lens siis the distance from the lens to the image f is the focal length of the lens Object • magnification of lens: So Si Image

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

10. 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

11. 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

12. • 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

13. 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(500nm)/(22.5/3600 x /180) = 0.56cm  8.644x102 W/m2 - the minimum power of a star collecting power of lens with the Signal-to-Noise Ratio >= 10, D >= 0.3648cm

14. • considered thin lenses when lens thickness<<focal length and the diameter of lens<<2 x radius of curvature of lens 3cm radius of curvature example: 3cm radius of curvature 3cm 3cm 1cm << 6cm 4.5cm lens diameter 1cm lens diameter plano-convex lens negligible thickness not negligible thickness

15. Design: f = 1cm CCD f = 3cm parallel rays: image at infinity 1.247cm 7.06cm 3cm both lens diameter =1cm blurspot size after first lens = 2.44/D = 3.66x10-6m Blurspot - central part of Airy disk desired blurspot size (to span 4 pixels) = 2x7.4m = 14.8x10-6m magnification factor needed = 4.044 7.4m