ESA's OGS is being upgraded with a complementary unit and, together with two US ground terminals, will relay data at unprecedented rates using infrared light beams at a wavelength similar to that used in fiber-optic cables on Earth. 7923, "Free-Space Laser Communication Technologies XXIII," San Francisco, CA, USA, Jan. 26, 2011, doi:10.1117/12.878927, 67) D. M. Boroson, J. J. Scozzafava, D. V. Murphy, B. S. Robinson, H. Shaw, "The Lunar Laser Communications Demonstration (LLCD)," Third IEEE International Conference on Space Mission Challenges for Information Technology (SMC-IT), Pasadena, CA, USA, July 19-23, 2009, URL: http://dspace.mit.edu/openaccess-disseminate/1721.1/61673, 68) John Rush, Ken Perko, "NASA Plan for Development of Optical Communication for Space Applications," May 15, 2009, URL: http://www.spacepolicyonline.com/pages/images/stories/Rush_NRC_Optical The body-fixed array design minimizes articulation on the spacecraft bus. A clamshell enclosure protects these telescopes from the weather during periods of inactivity. - The payload instrument measurements changed when LADEE swooped down to 50 km above the moon’s surface after OLM-3 on Nov. 10. Each gain stage is pumped with two external grating stabilized 976 nm pump lasers. The project is currently in elliptic orbits around Earth, called phasing loops, and will continue with two more of these elliptical orbits until LADEE is captured around the moon using an initial LOI-1 (Lunar Orbit Insertion-1) burn on Oct. 6, 2013. The Lunar Dust EXperiment (LDEX) team noted an increase in dust around the time of the landing. Useful data services were demonstrated and found to be dependable. - "The Moon doesn't have significant amounts of H2O or OH in its atmosphere most of the time," said Richard Elphic, the LADEE project scientist at NASA's Ames Research Center in California's Silicon Valley. LDEX observes both the impact ejecta and the population of dust lofted by plasma effects. An unusually large burst of events was observed on Nov. 12, 2013, most likely related to the Taurids meteor shower. LADEE continues to perform splendidly. • Dec. 11, 2013: LADEE completed its OLM-3 (Orbit Lowering Maneuver-3) on Nov. 10, and its OLM-4 on Nov. 20, 2013. Fast reset times (~15 ns) and small timing jitter (~60 ps FWHM) allow the SNSPD-based photon counting receiver to achieve high count rates with relatively few detector elements when compared to other technologies with similar detection efficiency. LDEX is designed to map the spatial and temporal variability of the dust size and density distributions in the lunar environment. Figure 1: Illustration of the LADEE orbiter (right) and the bus modules (left), image credit: NASA/ARC, Figure 2: Top view of the radiator assembly (image credit: NASA/ARC), Figure 3: Bottom view of the radiator assembly (image credit: NASA/ARC). The m/z of ions reaching the detector is a function of the voltage setting which allows the operator to select an ion with a particular mass-to-charge ratio to measure its abundance or run the instrument through a range of voltages to scan for a number of species that might be present. The encoder consists of a ½-rate serially concatenated PPM (Pulse Position Modulation) turbo code which is computed using a simple convolutional encoder and performs within 1.5 dB of the theoretical channel capacity. Additionally, LADEE NMS will observe the spatial distribution and temporal variability of species which condense at nighttime and show peak concentrations at the dawn terminator (e.g. The ranging turnaround function modulates the entire ranging channel, including noise onto the downlink. The Neutral mass Spectrometer (NMS) cap ejection on Oct. 3 was successful. • Instrument mass: 11.3 kg, envelope: 43.2 cm x 24.5 cm x 37.0 cm, power: 34.4 W average, data rate: 3.5 kbit/s. The closed source can be used for species that do not adsorb on surfaces within the ion source such as Helium, Argon and non-reactive neutrals as particles collide with the wall of the source multiple times prior to ionization. LADEE lacked fuel to maintain a long-term lunar orbit or continue science operations and was intentionally sent into the lunar surface. - In June 2013, the LADEE spacecraft arrived at NASA's Wallops Flight Facility to begin final processing for its trip to the moon. Figure 46: Block diagram of LLCD system architecture (image credit: MIT/LL), Tight size/weight/power constraints on the satellite payload (the average optical transmit power is < 1 W), in addition to the large R2 link loss due to the approximately 400 thousand kilometer separation between the earthbound ground terminal and lunar satellite, necessitate efficient usage of the optical signal appearing at the ground terminal receiver. Figure 23 shows a schematic representation of the mission system architecture and command and data flow within it (Ref. Contents: This version contains the reduced and calibrated data from the The individual components of the transmitter systems together with a block diagram are shown in Figure 52.The link margin for the communication uplink signal is given in Table 4. A separate electronics box in the Propulsion Module handles the valve driver actuation. The NMS instrument is based on a similar instrument on NASA's CoNTour (Comet Nucleus Tour) mission with a launch on July 3, 2002 and the SAM (Sample Analysis at Mars) instrument developed for the Mars Science Laboratory (MSL). Outside the linear region of the quadrant detector, the quality of the beam at the detector is not required to be perfect. The unambiguous identification of dust impacts is ongoing, based on the analysis of the individual waveforms. • Closed source species: He, Ar, non-reactive neutrals, • Mass resolution: unit mass resolution over entire range, • Sensitivity: 10-2 (counts per second) / (particles cm-3). The elements of the LADEE NMS are shown in Figure 11. 7993, "Free-Space Laser Communication Technologies XXIII," San Francisco, CA, USA, Jan. 26, 2011, doi:10.1117/12.878313, 66) Steven Constantine, Laura E. Elgin, Mark L. Stevens, Joseph A. Greco, Kenneth Aquino, Daniel D. Alves, Bryan S. Robinson, "Design of a high-speed space modem for the lunar laser communications demonstration," Proceedings of SPIE, Vol. - Until mid-April, ground controllers will continue to fire the LADEE altitude control thrusters once a week to keep the observatory in its target orbit. by measuring the physical properties of the particles impacting the The facilities are capable of providing particles with typical radii of 0.1 to 2 µm with speeds >> 10 km/s. For about 100 days, the spacecraft will gather detailed information about the structure and composition of the thin lunar atmosphere and determine whether dust is being lofted into the lunar sky.

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