&lt;title&gt;Laser communications terminal for the X2000 series of planetary missions&lt;/title&gt;

Hemmati, Hamid; Lesh, James R.

doi:10.1117/12.308707

Cited by 2 publications

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“…Currently, the SiC material is baselined for the telescope (structure, primary and secondary mirrors) material. The properties that make SiC attractive for the space optics applications include: (1) high specific stiffness & low mass; (2) very low thermal expansion coefficient (on the order of 1 ppm/K); (3) high thermal conductivity; (4) very high bending strength (400 Mpa) and low built in stress (< 0.1 Mpa); (5) it can withstand low and high temperatures without any loss of properties; (6) tests have shown that it is very insensitive to fatigue; (7) very high immunity to radiation; and (8) it can be easily ground and polished without distortions. Raw surface roughness is less than 0.5 mm and fme grinding can reduce it below 0.1 mm.…”

Section: 2e-17mentioning

confidence: 99%

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<title>Preliminary optomechanical design for the X2000 transceiver</title>

Hemmati

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1999

SPIE Proceedings

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Preliminary optical design and mechanical conceptual design for a 30 cm aperture transceiver are described.A common aperture is used for both transmit and receive.Special attention was given to off-axis and scattered light rejection and isolation of the receive channel from the transmit channel. Requirements, details of the design and preliminary performance analysis of the transceiver are provided.Keywords" Optical communication, optical design _TRODUCTIONA transceiver is designed for communication from the range of 6 AU to ground. The host spacect_ is of the type developed under the X2000 technology development program. A description of this program is given in Reference (1). The operation the transceiver consists of tracking a laser beacon from the earth or the sun-illuminated earth image beacon, and transmitting a signal back to the ground station.To minimize coordinate transfer errors between the tracking and transmit channels, and to minimize the size and complexity of the transceiver, the same aperture is used for both transmit and receive signals. An optical block diagram for the transceiver is shown in Figure I. For laser beacon tracking the transmit and receive signals differ by 532 nm. However, for extendedsource earth image tracking the broad-band spectrum of the sun overlaps the 1064 nm laser transmit wavelength.This design is based on the Optical Communication Demonstrator (OCD) architecture. An overview of the OCD instrument can be found in Reference 2. The optical system consists of four optical channels.. TransmitChannel. This channel consists of an optical path to relay a transmit signal fi'om the output of the laser transmitter to the exit aperture of the optics. The transit optical path must provide fine-pointing capability to control the downlink over the entire system field-of-view.The transmit path must maintain good beam quality over the entire fieldof-view. . Data Detector Receive Channel.This channel consists of a receive optical path to collect the incident photon from the input aperture to the data detector. The receive optical path must provide narrow-band filtering to reduce the amount d" background radiation, and must provide the field-of-view necessary to cover the spacecraft deadband cycle. Furthermore, the receive optical path must provide sufficient isolation such that the effect of signal feedback from the transmit path is minimized.Wavefront quality is not essential for the receive path. However, matching a wide field-of-view to a small diameter detector poses significant challenges to the optical design.. TrackingReceive Channel. This channel consists of an optical path that images the field-of-view onto the celestial reference detector.This detector is currently baselined to be a 1024x!024 array with 20 micron pixel size, and covers the 9 mrad x 9 mrad field-of-view.The receive optics should provide intentional blurring of the image to spread the tracking signal over 2-3 pixels. However, it must be void of coma and other non-symmetric aberration patterns.. Tracking ...

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Section: 2e-17mentioning

confidence: 99%

“…The host spacecraft is of the type developed under the X2000 technology development program. A description ofthis prOgram is given in Reference (1). The operation d' the transceiver consists oftracking a laser beacon from the earth or the sun-illuminated earth image beacon, and transmitting a signal back to the ground station.…”

Section: Introductionmentioning

confidence: 99%