Liquid crystal spatial light modulators are emerging as a potential replacement to traditional optical beam steering methods. The performance of these devices for optical communication systems in the radiation environment for geostationary orbits (GEO) are of interest for applications in the next generation of satellites. As an initial investigation to the study presented, several liquid crystals were irradiated to total dose levels consistent with expected GEO environments. While prior irradiation work has been done on spatial light modulators none is known to include a first look at a liquid crystal and CMOS backplane. Parameters of retardation, contrast ratio and primary power current were monitored at incremental stages during the test and are presented.
Charge Injection Devices (CIDs) have historically played a niche role in visible imager technologies, mainly for applications requiring high radiation tolerance. They have not exhibited the radiometric performance of competing visible- imaging technologies such as CCDs, and so have not been widely applied to space instrument systems. Recent advances in CIDs have demonstrated much higher radiometric performance as well as lower noise operation, without compromising the radiation tolerance of the devices, making the devices suitable for a wide range of space instruments. We present radiometric, noise, and radiation response data for several of the newest CID designs that are candidate technologies for visible space telescope systems.
Commercial high speed fiber optic transmitters and receivers were tested in a high energy proton environment at the Crocker Nuclear Laboratory to determine the transient impact of the space proton environment on a simulated communications link. The link was designed to simulate free-space communication between satellites. The transmit/receive bit error ratio was used as the evaluation metric. Individual electronic components on each transmitter and receiver module were tested using a variety of proton energies, angles of incidence, and optical link configurations. No change was found in the bit error ratio for any of the transmitters tested. Significant increases in bit error ratio were found on two of the receivers when several individual receiver components were irradiated. Small increases in bit error ratio were found on several receivers when exposed to 63 MeV proton fluxes greater than 1 X 107 p/cm2-s. The remaining receivers were found to be immune to the influence of the protons. This testing demonstrates the feasibility of operating commercial transmitters and receivers in a free-space optical link when exposed to the space proton environment.
Experiments were conducted to evaluate the viability of commercial-off-the-shelf (COTS) technology in the design of high-performance optical intersatellite communications links. The optical links were operated at 155, 622 and 2488 Megabits per second (Mbps) and at 1550 nm wavelength. Communications components were evaluated against performance parameters for on-off keyed (OOK) systems. Transmitters, receivers, optical amplifiers, and filters, used to minimize the impact of amplified spontaneous emission (ASE), were characterized individually and within system configurations. Bit error rate (BER) as a function of photons per bit was characterized for several system configurations. Extinction ratio analysis experiments were conducted to determine the limiting factors on the systems performance. Widely varying optical powers in space (for low earth orbit) imply a robust receiver dynamic range requirement. Dynamic range of COTS receivers was examined and resulted in sufficient performance. In addition, gamma radiation tests on fiber amplifiers were also evaluated in a system context.
Conference Committee Involvement (4)
Focal Plane Arrays for Space telescopes IV
2 August 2009 | San Diego, California, United States
Focal Plane Arrays for Space Telescopes III
28 August 2007 | San Diego, California, United States
Focal Plane Arrays for Space Telescopes II
3 August 2005 | San Diego, California, United States
Focal Plane Arrays for Space Telescopes
5 August 2003 | San Diego, California, United States
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