urn:nasa:pds:context:instrument:lro.rss 1.0 1.11.0.0 Product_Context urn:nasa:pds:context:instrument:rss.lro 2021-02-24 1.0 Changed inst LIDs from u:n:p:c:i:instID.scID to u:n:p:c:i:scID.instID And per "Guide toPDS4 Context Products" v1.7, changed all lidvid_reference to lid_reference urn:nasa:pds:context:instrument_host:spacecraft.lro instrument_to_instrument_host Chin, G., et al., Lunar Reconnaissance Orbiter Overview: The Instrument Suite and Mission, Space Sci. Rev. 129:391-419, 2007. reference.CHINETAL2007 Nguyen, Q., W. Yuknis, S. Pursley, N.Haghani, D. Albaijes, and O. Haddad, A High Performance Command and Data Handling System for NASA's Lunar Reconnaissance Orbiter, American Institute of Aeronautics and Astronautics, 9-11 September 2008. reference.NGUYENETAL2008 Pearlman, M., C. Noll, J. McGarry, W. Gurtner, and E. Pavlis, The International Laser Ranging Service, AOGS Advances in Geosciences: Solid Earth, 2008. reference.PEARLMANETAL2008 Smith, D.E., M.T. Zuber, G.B. Jackson, G.A. Neumann,H. Riris, X. Sun, R.S. Zellar, C. Coltharp, J. Connelly, R.B. Katz, I. Kleyner, P. Liiva, A. Matuszeski, E.M. Mazarico, J.F. McGarry, A.-M. Novo-Gradac, M.N. Ott, C. Peters, L.A. Ramos-Izquierdo, L. Ramsey, D.D. Rowlands, S. Schmidt, V.S. Scott III, G.B. Shaw, J.C. Smith, J.-P. Swinski, M.H. Torrence, G. Unger, A.W. Yu, T.W. Zagwodzki, The Lunar Orbiter Laser Altimeter Investigation on the Lunar Reconnaissance Orbiter Mission, Space Science Reviews, 16 May 2009. reference.SMITHETAL2009 Tooley, C.R., M.B. Houghton, R.S. Saylor, Jr., C. Peddie, D.F. Everett, C.L. Bakerk and K.N. Safdie, Lunar Reconnaissance Orbiter Mission and Spacecraft Design, Space Sci. Rev. 150:23-62, 2010. reference.TOOLEYETAL2010 Zuber, M.T., D.E. Smith, R.S. Zellar, G.A. Neumann, X. Sun, R.B. Katz, I. Kleyner, A. Matuszeski, J.F. McGarry, M.N. Ott, L.A. Ramos-Izquierdo, D.D. Rowlands, M.H. Torrence and T.W. Zagwodzki, The Lunar Reconnaisance Orbiter Laser Ranging Investigation, Space Science Reviews, 16 May 2009. reference.ZUBERETAL2009 RADIO SCIENCE SUBSYSTEM Atmospheric Sciences not applicable not applicable Instrument Overview =================== The communication, tracking, and timekeeping systems on LRO support the generation of the precise geolocation needed by the LRO science and measurement investigations. The information provided by these systems is similar to conventional Radio Science data, although traditional 'radio science' was not an initial mission objective. The importance of the tracking data for all of the other investigations merits its being archived for completeness and future analysis. Radio Doppler and range tracking to the LRO omnidirectional and high-gain antennas (HGA) provides the main source of the radio science data. The gimbaled HGA also carries a small, coboresighted, optical receiver telescope. One-way time-of-flight from the ground to the optical receiver using laser pulses provides an alternate tracking data type known as Laser Ranging (LR), which is handled jointly by the Lunar Orbiter Laser Altimeter (LOLA) Science Operations Center (SOC) and the Crustal Dynamics Data Information System (CDDIS). The spacecraft Radio Frequency subsystems are described herein and in more detail in [TOOLEYETAL2010]. The LR subsystem is described in [ZUBERETAL2009], and in the LOLA instrument description [SMITHETAL2009]. The ground elements consist of the commercial Universal Space Network (USN), the Ka-band ground station at White Sands, New Mexico (WS1), and the Next Generation Satellite Laser Ranging station in Greenbelt, Maryland (NGSLR). Additional data were provided by the NASA Deep Space Network (DSN) during commissioning. Ongoing participation by the International Laser Ranging Service (ILRS) network of stations provides further LR data that are processed by the LOLA SOC. Communication Subsystem ----------------------- LRO's communications system consists of an S-band system to provide tracking, telemetry and commanding (TT&C) and a high data rate Ka-band, downlink-only system for telemetry and science data transfers. The S-Band system has a fixed forward link data rate of 4 kbps, and a selectable on-orbit return link data rate between 125 bps and 1093 kbps. It consists of one Spacecraft Tracking and Data Network (STDN) compatible transponder, an S-band Radio Frequency (RF) Switch, and the RF paths to and from the two Omni-Directional antennas and the S- band feed on the High Gain Antenna (HGA). The transponder downlinks at a frequency which is phase-locked to the uplink, providing two-way Doppler tracking information to the ground with an accuracy of better than 1 mm/s. It also repeats uplinked range tones with a fixed delay, allowing the ground to determine the distance to the Orbiter within 15 m. The Ka-band system includes a Ka-Band modulator, a Traveling Wave Tube Amplifier (TWTA) consisting of a traveling wave tube (TWT), an Electronic Power Conditioner (EPC), and a High Power Isolator. The Ka-band return link is also selectable on orbit and varies from 25 Mbps to 100 Mbps. Although the Ka-band system uses only the High Gain Antenna, the S-band system can utilize either the Omni-Directional or the High Gain Antenna for transmit and always uses both paths for receiving. The ground selects the uplink path via polarization, as the HGA has opposite polarization from the omni antennas for this reason. Specifications for each of the S- and Ka-Band subsystems are given in [TOOLEYETAL2010]. In brief, frequency, polarization, and RF transmit power for the spacecraft are: S-Band System: 2271.2 +/- 2.5 MHz (Transmit), 2091.3967 +/- 2.5 MHz (Receive); Left Hand Circular Polarization (Omni) Right Hand Circular Polarization (HGA) 5.8 Watt Diplexers Ka-Band System: 25.65 GHz +/- 150 MHz (Transmit) Left Hand Circular Polarization 41.9 Watt TWTA Output The S-Comm card is designed to accommodate a telemetry interface to Earth using S-Band frequencies. The S-Comm card is connected directly to the Single Board Computer (SBC) via a 10 Mbps SpaceWire link [NGUYENETAL2008]. During a ground station pass the data from the SBC flow directly into the S-Comm card and are encoded for transmission per CCSDS recommendations for telemetry encoding using concatenated encoding. The S-Comm provides one telemetry stream at up to 1.093 Mbps to the transmitter for Bi-Phase Shift Keying (BPSK) modulation onto the RF carrier.The S-Comm accepts uplinked CCSDS telecommands from the S-Band transponder at 4 Kbps. Normally commands are forwarded to the SBC for further processing via the SpaceWire interface unless they are tagged as hardware-decoded commands. Hardware- decoded commands are performed directly by the S-Comm card. The S-Comm card can support up to 8 hardware-decoded commands, 4 of which are RS-422 outputs. Hardware- decoded commands are only used in contingency situations.Both the S-comm and Ka-comm card provide control of the respective Communication Subsystem transmitters via asynchronous low rate serial interfaces. LRO makes use of a global network of S-band ground stations for nominal spacecraft tracking (at least 30 minutes per orbit) and one Ka-band station for downlink of all the stored instrument and spacecraft data. Nominally, LRO is never be out of contact with the ground for more than one hour at a time. Station-keeping maneuvers and instrument calibrations occur once a month. Momentum management maneuvers occur every 2 weeks. There is an S-band pass every orbit (12 per day), and 4 (on average) Ka-band passes between LRO and WS1 every day, each lasting 45 minutes. The actual number fluctuates between 2 and 6, as the Moon moves through its entire declination range each month (as seen from the Earth). Most of the instruments operate autonomously over the course of a single orbit, while two (LROC and Mini-RF) require daily tailored command timelines. Nominally, LRO receives a new command timeline from the ground once per day that includes tracking schedules and antenna targets. Ultra Stable Oscillators (USO) ------------------------------ The C&DH subsystem includes both a primary and a redundant USO to provide precision timekeeping onboard the spacecraft. Each oscillator provides two 20-MHz signals. One signal goes to the C&DH HK/IO card and the second goes directly to the LOLA instrument. Only one of the oscillators is powered at any given time. The primary USO has a frequency stability factor of 10 parts per billion (ppb) over one millisecond (ms). It was chosen to provide sufficient stability to meet the needs of the laser ranging system. It receives a +31VDC switched service from the Power Subsystem Electronics (PSE). The redundant USO has a frequency stability factor of 0.3 parts per million (ppm) over one millisecond (ms). It was chosen to provide sufficient stability to meet the needs for LOLA reconstruction of the orbital ephemeris. It receives a +15VDC switched service from the LVPC. Data Downlink ------------- The LRO flight computer is a RAD-750 processor executing at 133 MHz. Two 100 Gbyte recorders store science data for playback to the earth at 100 Mbps. An S-band system provides command, engineering telemetry, and navigation functions. On a given day, about 460 Gbits of data are generated on-board the LRO spacecraft. Data are downlinked at 100 Mbps through a single Ka-band ground station at White Sands, New Mexico, USA (designated WS1). Even in the worst case (2 passes), there is sufficient time to downlink the entire day's data volume. Active One-Way Laser Ranging System ----------------------------------- During the preliminary design phase an active one-way (uplink) laser ranging system was added to LRO to improve the tracking, and thus geodetic accuracy of the data products, over that possible with the S-Band tracking system alone. The elements of the active laser ranging system include a ground station at GSFC, which transmits a 532 nm pulse at 28 Hz. This pulse is captured by the laser ranging telescope mounted on the high gain antenna and then transmitted via fiber optic cable to the LOLA detector assembly. Time-stamped arrival and departure times allow for precise range measurements from Earth to the LRO spacecraft, thus helping to determine precise position relative to the Earth's surface. Those data, combined with known positioning of the spacecraft and LOLA data gathered from the Moon, provide enough information to improve the lunar gravity modeling which can, in turn, be used to improve the orbit determination. Passive Two-Way Laser Ranging System ------------------------------------ In addition to the active laser ranging system LRO carries a retro-reflector assembly consisting of twelve 1-inch-diameter solid retro-reflective prisms in a square array mounted on the -Z face (zenith radiator). This retro- reflector allows high-power terrestrial laser ranging sites to perform two-way laser ranging to LRO. This ranging is conducted as an experiment of opportunity late in the mission. The HGA must be parked for safety and to provide visibility to the retro-reflector assembly from Earth. As well, the array must point within approximately 20 degrees of Earth, which is only possible for a few days a month while LRO is in mapping configuration. Ground stations --------------- The baseline tracking system for LRO is an S-band (2.2-2.3 GHZ) radio frequency link for approximately ~20 hours per day [CHINETAL2007]. A commercial network, the Universal Space Network (USN), provides tracking with stations at Dongara, Australia; Kiruna, Sweden; Weilham, Germany; and South Point, Hawaii. The Doppler accuracy of the USN is ~1 mm/s (one sigma) averaged over 10 s, which for the tracking time allocated permits LRO orbits to be determined to approximately ~10 m radially and 300 m along-track and across-track. Several ILRS stations [PEARLMANETAL2008] participate in the LR investigation as ground stations. The addition of ILRS stations provides global coverage for LR and increases the laser ranging data set. A few of the participating ILRS stations are also synchronizing their laser fires to the LOLA Earth window in a similar manner to NGSLR, while several others are firing asynchronously at 5 or 10 Hz. At 10 Hz only 2 to 4 pulses per second fall in the LOLA Earth window. The remaining 6-8 pulses are treated as noise by LOLA, but these are not enough to cause significant disruptions to the LOLA measurements. Since this is an uplink-only ranging measurement, there is no real-time feedback of spacecraft tracking as in normal SLR operations. Instead, LOLA's real-time housekeeping telemetry is used to provide needed feedback to the stations. LOLA's onboard signal processing indicates whether the Earth pulses are arriving at LRO, and in addition tracks the time at which these pulses occur within the Earth window. The LOLA Earth energy monitor also provides an integrated energy over each Earth window. This information is posted in graphical form to a password protected website that provides feedback to all participating stations. The delay between spacecraft event and webpage plot should be less than 30s. NGSLR is able to bias its fire times from this information to: (1) search for the Earth window if no signal is seen in the LOLA housekeeping telemetry, and/or (2) ensure that its laser pulses are arriving as early as possible in the single-stop Earth window. Appendix -------- The USN station positions are given in the table below, in geographic coordinates (WGS-84 Ellipsoid): Name / idstation / lat (ddmmss.ss) / lon (ddmmss.ss) / altitude (m) ------------------------------------------------------------------- KU1S 1 126 67 53 22.4100 21 03 56.3571 400.400 Kiruna KU2S 1 127 67 52 59.4570 21 03 37.6140 442.000 Kiruna WU1S 1 128 47 52 48.2500 11 05 07.0890 663.392 Weilheim WU2S 1 129 47 52 52.3160 11 05 01.0280 663.374 Weilheim USHS 1 105 19 00 50.0562 204 20 12.1155 385.194 Hawaii USPS 1 103 -29 02 44.7798 115 20 55.2395 250.470 Dongara The body-fixed coordinates of the tracking stations (X, Y, Z): Name Code Coordinates (x,y,z; km) -------------------------------------------------------- USN_Kiruna_1 KU1S 2246.85161 865.44085 5886.83851 USN_Kiruna_2 KU2S 2247.55970 865.47907 5886.60934 USN_Wilheim_1 WU1S 4206.09325 824.08227 4708.43445 USN_Wilheim_2 WU2S 4206.02603 823.94076 4708.51867 USN_Hawaii USHS -5496.58634 -2486.04351 2064.93016 USN_Dongara USPS -2389.19709 5043.29132 -3078.45895 White_Sands WS1S -1539.02700 -5158.58418 3411.91754 The data downlink stations are: Name Code Coordinates (x,y,z; km) --------------------------------------------------------------- White_Sands_Ka_band WS1K -1539.02700 -5158.58418 3411.91754 SDO_backup_Ka_band STSK -1539.01044 -5158.52883 3412.00723 Some DSN or other network stations that participated during commissioning: Name Code Coordinates (x,y,z; km) ---------------------------------------------------------------- DSN_Goldstone_24 DS24 -2354.90671 -4646.84008 3669.24232 DSN_Canberra_34 DS34 -4461.14709 2682.43924 -3674.39313 DSN_Madrid_54 DS54 4849.43449 -360.72390 4114.61884 Coordinates of Laser Ranging stations that track the LRO HGA: Name Code ID Coordinates (x,y,z; km) ----------------------------------------------------------------------- LR_Greenbelt_NGSLR GO1L 7125 1130.74360 -4831.37152 3994.07940 LR_Greenbelt_MOBLAS7 GODL 7105 1130.719703 -4831.350572 3994.106526 LR_Hartebeesthoek_SA HARL 7501 5085.40368 2668.33144 -2768.69029 LR_McDonald_Texas MDOL 7080 -1330.0210 -5328.4018 3236.4807 LR_Monument_Peak_CA MONL 7110 -2386.27943 -4802.35655 3444.88331 LR_Zimmerwald_Swtzlnd ZIML 7810 4331.28368 567.54974 4633.14027 LR_Herstmonceaux_UK HERL 7840 4033.46371 23.66248 4924.30517 LR_Grasse_France GRSM 7845 4581.69218 556.19602 4389.35507 LR_Wettzel_Germany WETL 7834 4075.57685 931.78546 4801.58356 LR_Yarragadee_AU YARL 7090 -2389.00813 5043.33184 -3078.52644