urn:nasa:pds:context:instrument:dif.rss 1.0 1.11.0.0 Product_Context urn:nasa:pds:context:instrument:rss.dif 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.dif instrument_to_instrument_host Anderson, J.D., J.W. Armstrong, and E.L. Lau, Upper Limits for Gravitational Radiation from Supermassive Coalescing Binaries, Astrophysical Journal, 408, 287-292, 1993. reference.ANDERSONETAL1993 Asmar, S.W., and R.G. Herrera, Radio Science Handbook, JPL D-7938, Volume 4, Jet Propulsion Laboratory, Pasadena, CA, 22 January 1993. reference.ASMAR-HERRERA1993 Asmar, S. W., N. A. Renzetti, The Deep Space Network as an instrument for radio science research, NASA Technical Reports Server, 1993STIN...9521456A, 1993. reference.ASMAR-RENZETTI1993 Asmar, S.W., R.G. Herrera, and T. Priest, Radio Science Handbook, JPL D-7938, Volume 6, Jet Propulsion Laboratory, Pasadena, CA, 1995. reference.ASMARETAL1995 Boucher, C., Z. Altamimi, and L. Duhem, IERS Technical Note 18, Results and Analysis of the ITRF93, Central Bureau of the International Earth Rotation Service, Observatoire de Paris, October 1994. reference.BOUCHERETAL1994 Deep Space Network / Flight Project Interface Design Book, Document 810-5, Jet Propulsion Laboratory, Pasadena, CA. reference.DSN810-5 Deep Space Mission Systems, Tracking and Navigation Service, Requirements and Design, DSMS No. 821-104, Rev. B, JPL D-17235, Jet Propulsion Laboratory, Pasadena, CA, 2003. reference.DSN821-104 Deep Space Mission Systems, Radio Science Service, Requirements and Design, DSMS No. 821-110, Rev. A, JPL D-17241, Jet Propulsion Laboratory, Pasadena, CA, 2001. reference.DSN821-110 Deep Space Mission System / Cassini Project Network Operations Plan, March 2003. reference.DSN871-011 Estabrook, F.B., and H.D. Wahlquist, Response of Doppler Spacecraft Tracking to Gravitational Radiation, Gen. Rel. Grav., 6, 439-447, 1995. reference.ESTABROOKETAL1995 Hinson, D.P., R.A. Simpson, J.D. Twicken, G.L. Tyler, and F.M. Flasar, Initial Results from Radio Occultation Measurements with Mars Global Surveyor, Journal of Geophysical Research, 104, 26997-27012, 1999. reference.HINSONETAL1999 Smith, D.E., M.T. Zuber, S.C. Solomon, R.J. Phillips, J.W. Head, J.B. Garvin, W.B. Banerdt, D.O. Muhleman, G.H. Pettengill, G.A. Neumann, F.G. Lemoine, J.B. Abshire, O. Aharonson, C.D. Brown, S.A. Hauck, A.B. Ivanov, P.J. Mcgovern, H.J. Zwally, and T.C. Duxbury, The Global Topography of Mars and Implications for Surface Evolution, Science, Vol. 284, pp. 1495-1503, 1999. reference.SMITHETAL1999B Smith, D.E., W.L. Sjogren, G.L. Tyler, G. Balmino, F.G. Lemoine, and A.S. Konopliv, The Gravity Field of Mars: Results from Mars Global Surveyor, Science, 286, 94-97,1999. reference.SMITHETAL1999C Smith, D.E., M.T. Zuber, R.M. Haberle, D.D. Rowlands, and J.R. Murphy, The Mars Seasonal CO2 Cycle and the Time Variation of the Gravity Field: A General Circulation Model Simulation, Journal of Geophysical Research, 104, 1885-1896, 1999. reference.SMITHETAL1999D Tyler, G.L., G. Balmino, D.P. Hinson, W.L. Sjogren, D.E. Smith, R. Woo, S.W. Asmar, M.J. Connally, C.L. Hamilton, and R.A. Simpson, Radio Science Investigations with Mars Observer, Journal of Geophysical Research, 97, 7759-7779, 1992. reference.TYLERETAL1992 Woo, R., Spacecraft Radio Scintillation and Solar System Exploration, Wave Propagation in Random Media (Scintillation), Society of Photo-Optical Instrumentation Engineers, Bellingham, WA, 1993. reference.WOO1993 Yeomans, D.K., J.D. Giorgini, and S.R. Chesley, The History and Dynamics of Comet 9P/Tempel 1, Space Science Reviews, 117, 123-135, 2005, doi:10.1007/s11214-005-3392-6. reference.YEOMANSETAL2005 RADIO SCIENCE SUBSYSTEM Atmospheric Sciences not applicable not applicable Instrument Overview =================== The DI comet Tempel 1 flyby Radio Science investigations utilized instrumentation with elements on the spacecraft and at the NASA Deep Space Network (DSN). Much of this was shared equipment, being used for routine telecommunications as well as for Radio Science. The performance and calibration of both the spacecraft and tracking stations directly affected the radio science data accuracy, and they played a major role in determining the quality of the results. The spacecraft part of the radio science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Specifications - Spacecraft ====================================== The DI comet Tempel 1 flyby spacecraft telecommunications subsystem served as part of a radio science subsystem for investigations of Tempel 1. Many details of the subsystem are unknown; its 'build date' is taken to be 1995-02-01, the date on which acceptance testing began at Ball. Instrument Id : RSS Instrument Host Id : DI Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : 1995-02-01 Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : Motorola Instrument Overview - Spacecraft ================================ The DI flyby spacecraft radio system operates at X-band through the DSN 34 m (BWG) and 70 m nets to receive commands, downlink telemetry and provide tracking for navigation. There are two low, and one high gain X-band antennas, two small deep-space transponders and a pair of 20W TWTA power amplifiers. The X-band capability reduced plasma effects on radio signals by a factor of 10 compared with previous S-band systems, but absence of a dual-frequency capability (both S- and X-band) meant that plasma effects could not be estimated and removed from radio data. The HGA was a 1.0 m diameter dish of a Cassegrain design that was directed in the spacecraft's +Z direction. Science Objectives ================== Because of the relatively distant flyby (close approach = 500 km) of the DI spacecraft past the nucleus of comet Tempel 1 and the rapid relative velocity of the flyby (10.1 km/s), there was not expected to be any indication of the spacecraft's deflection due to the neighboring comet mass nor was there expected to be any indication that the spacecraft was slowed down as a result of gas and dust drag upon the spacecraft. Both of these expectations came to pass (i.e., no effects noted in the tracking data). Yet, it is not out of the question that future researchers will find a use for these tracking data. Operational Considerations - Spacecraft ======================================= Descriptions given here are for nominal performance. The spacecraft transponder system comprised redundant units, each with slightly different characteristics. As transponder units age, their performance changes slightly. Their performance also depends upon factors which were not always under the control of the DI Project. Calibration Description - Spacecraft ==================================== No information available. Platform Mounting Descriptions - Spacecraft =========================================== The spacecraft +Z axis vector was aligned with the HGA boresight perpendicular to the top surface of the spacecraft. The +Y axis vector ran through the power switching electronics box and the +X axis completed the orthogonal, right-handed, rectangular coordinate system. The axes of the two low gain antennas were in the +Z and -Z directions. Investigators ============= Team Leader for the DI Radio Science Team was D.K. Yeomans of the Jet Propulsion Laboratory (JPL). Collaborating on this investigation were Jon D. Giorgini and Steve R. Chesley, Instrument Overview - DSN ========================= Three Deep Space Communications Complexes (DSCCs) (near Barstow, CA; Canberra, Australia; and Madrid, Spain) comprise the DSN tracking network. Each complex is equipped with several antennas [including at least one each 70-m, 34-m High Efficiency (HEF), and 34-m Beam WaveGuide (BWG)], associated electronics, and operational systems. A primary activity at each complex is radiation of commands to and reception of telemetry data from active spacecraft. Transmission and reception are possible in several radio frequency bands; the most common are S-band (nominally a frequency of 2100-2300 MHz, or a wavelength of 14.2-13.0 cm) and X-band (7100-8500 MHz, or 4.2-3.5 cm). Transmitter output powers of up to 100 kW S-band and 20 kW X-band are available. Ground stations have the ability to transmit coded and uncoded waveforms which can be echoed by distant spacecraft. Analysis of the received coding allows navigators to determine the distance to the spacecraft; and analysis of Doppler shift on the carrier signal allows estimation of the line-of-sight spacecraft velocity. Range and Doppler measurements are used to calculate the spacecraft trajectory and to infer gravity fields of objects near the spacecraft. Ground stations can record spacecraft signals that have propagated through or been scattered from target media. Measurements of signal parameters after wave interactions with surfaces, atmospheres, rings, and plasmas are used to infer physical and electrical properties of the target. The Deep Space Network (DSN) is managed by the Jet Propulsion Laboratory (JPL) of the California Institute of Technology for the U.S. National Aeronautics and Space Administration (NASA). Specifications include: Instrument Id : RSS Instrument Host Id : DSN Pi Pds User Id : N/A Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : N/A Instrument Mass : N/A Instrument Length : N/A Instrument Width : N/A Instrument Height : N/A Instrument Manufacturer Name : N/A For more information on the Deep Space Network and its use in radio science see reports by [ASMAR&RENZETTI1993], [ASMAR&HERRERA1993], and [ASMARETAL1995]. For design specifications on DSN subsystems see [DSN810-5]. Subsystems - DSN ================ The Deep Space Communications Complexes (DSCCs) are an integral part of Radio Science instrumentation, along with the spacecraft RFS and RFIS. Their system performance directly determines the degree of success of Radio Science investigations, and their system calibration determines the degree of accuracy in the results of the experiments. The following paragraphs describe the functions performed by the individual subsystems of a DSCC. This material has been adapted from [ASMAR&HERRERA1993] and [DSN871-011]; for additional information, consult [DSN810-5], [DSN821-110], and [DSN821-104]. Each DSCC includes a set of antennas, a Signal Processing Center (SPC), and communication links to the Jet Propulsion Laboratory (JPL). The general configuration is illustrated below. -------- -------- -------- -------- -------- | DSS 25 | | DSS 27 | | DSS 14 | | DSS 15 | | DSS 16 | |34-m BWG| |34-m HSB| | 70-m | |34-m HEF| | 26-m | -------- -------- -------- -------- -------- | | | | | | v v | v | --------- | --------- --------->|GOLDSTONE|<---------- |EARTH/ORB| | SPC 10 |<-------------->| LINK | |---------| |---------| | SPC |<-------------->| 26-M | | COMM | ------>| COMM | --------- | --------- | | | v | v ------ --------- | --------- | NOCC |<--->| JPL |<------- | | ------ | CENTRAL | | GSFC | ------ | COMM | | NASCOMM | |AMMOS |<--->| TERMINAL|<-------------->| | ------ --------- --------- ^ ^ | | CANBERRA (SPC 40) <---------------- | | MADRID (SPC 60) <---------------------- The following table gives a list of the current DSN antennas (Deep Space Stations, or DSSs -- a term carried over from earlier times when antennas were individually instrumented). GOLDSTONE CANBERRA MADRID Antenna SPC 10 SPC 40 SPC 60 -------- --------- -------- -------- 26-m DSS 16 DSS 46 DSS 66 34-m HEF DSS 15 DSS 45 DSS 65 34-m BWG DSS 24 DSS 34 DSS 54 DSS 25 DSS 55 DSS 26 34-m HSB DSS 27 DSS 28 70-m DSS 14 DSS 43 DSS 63 Developmental DSS 13 Subsystem interconnections at each DSCC are shown in the two diagrams below, and are described in the sections that follow. The first diagram is for the pre-NSP (Network Simplification Project) era, and the second diagram is for the post-NSP era. NSP implementation took place over a period of about 5 months in 2003 (from January through May). The Monitor and Control Subsystem is connected to all other subsystems; and the Test Support Subsystem can be. Pre-NSP DSCC ------------ ----------- ------------------ --------- --------- |TRANSMITTER|_| |_| TRACKING|_| COMMAND |_ | SUBSYSTEM | | | |SUBSYSTEM| |SUBSYSTEM| | ----------- | RECEIVER-EXCITER | --------- --------- | | | SUBSYSTEM | | | | ----------- | | --------------------- | | MICROWAVE |_| |_| TELEMETRY |_| | SUBSYSTEM | | | | SUBSYSTEM | | ----------- ------------------ --------------------- | | | ----------- ----------- --------- -------------- | | ANTENNA | | MONITOR | | TEST | | DIGITAL |_| | SUBSYSTEM | |AND CONTROL| | SUPPORT | |COMMUNICATIONS| ----------- | SUBSYSTEM | |SUBSYSTEM| | SUBSYSTEM | ----------- --------- -------------- Post-NSP DSCC ------------- ----------- ------------------ --------------------- |TRANSMITTER|_| UPLINK |_| COMMAND |_ | SUBSYSTEM | | SUBSYSTEM | | SUBSYSTEM | | ----------- ------------------ --------------------- | | | ----------- ------------------ --------------------- | | MICROWAVE |_| DOWNLINK |_| TELEMETRY |_| | SUBSYSTEM | | SUBSYSTEM | | SUBSYSTEM | | ----------- ------------------ --------------------- | | | ----------- ----------- --------- -------------- | | ANTENNA | | MONITOR | | TEST | | DIGITAL |_| | SUBSYSTEM | |AND CONTROL| | SUPPORT | |COMMUNICATIONS| ----------- | SUBSYSTEM | |SUBSYSTEM| | SUBSYSTEM | ----------- --------- -------------- DSCC Monitor and Control Subsystem ---------------------------------- The DSCC Monitor and Control Subsystem (DMC) is part of the Monitor and Control System (MON) which also includes the ground communications Central Communications Terminal (CCT) and the Network Operations Control Center (NOCC) Monitor and Control Subsystem. The DMC is the center of activity at a DSCC. The DMC receives and archives most of the information from the NOCC needed by the various DSCC subsystems during their operation. Control of most of the DSCC subsystems, as well as the handling and displaying of any responses to control directives and configuration and status information received from each of the subsystems, is done through the DMC. The effect of this is to centralize the control, display, and short-term archiving functions necessary to operate a DSCC. Communication among the various subsystems is done using a Local Area Network (LAN) hooked up to each subsystem via a network interface unit (NIU). DMC operations are divided into two separate areas: the Complex Monitor and Control (CMC) and the Network Monitor and Control (NMC). The primary purpose of the CMC processor for Radio Science support is to receive and store all predict sets transmitted from NOCC -- such as antenna pointing, tracking, receiver, and uplink predict sets -- and then, at a later time, to distribute them to the appropriate subsystems via the LAN. Those predict sets can be stored in the CMC for a maximum of three days under normal conditions. The CMC also receives, processes, and displays event/alarm messages, and maintains an operator log. Assignment and configuration of the NMCs is done through the CMC; to a limited degree the CMC can perform some of the functions performed by the NMC. There are two CMCs (one on-line and one backup) and three NMCs at each DSCC. The backup CMC can function as an additional NMC if necessary. The NMC processor provides the operator interface for monitor and control of a link -- a group of equipment required to support a spacecraft pass. For Radio Science, a link might include one or more Radio Science Receivers (RSRs), the DSCC Tracking Subsystem (DTK), and special equipment required for Ka-band uplink and/or downlink (i.e., aberration correction, monopulse receiver, and advanced media calibration system). The NMC also maintains an operator log which includes all operator directives and subsystem responses. One important Radio Science-specific function that the NMC performs is receipt and transmission of the system temperature and signal level data from the PPM, for display at the NMC console and for inclusion in Monitor blocks. These blocks are recorded on magnetic tape as well as appearing in the NOCC displays. The NMC is required to operate without interruption for the duration of the Radio Science data acquisition period. The Area Routing Assembly (ARA), which is part of the Digital Communications Subsystem, controls all data communication between the stations and JPL. The ARA receives all required data and status messages from the NMC/CMC, and can record them to tape as well as transmit them to JPL via data lines. The ARA also receives predicts and other data from JPL, and passes them on to the CMC. DSCC Antenna Mechanical Subsystem --------------------------------- Multimission Radio Science activities require support from the 70-m, 34-m HEF, and 34-m BWG antenna subnets. The antennas at each DSCC function as large-aperture collectors which, by double reflection, cause the incoming radio frequency (RF) energy to enter the feed horns. The large collecting surface of the antenna focuses the incoming energy onto a subreflector, which is adjustable in both axial and angular position. These adjustments are made to correct for gravitational deformation of the antenna as it moves between zenith and the horizon; the deformation can be as large as 7 cm. The subreflector adjustments optimize the channeling of energy from the primary reflector to the subreflector, and then to the feed horns. The 70-m and 34-m HEF antennas have 'shaped' primary and secondary reflectors, with forms that are modified paraboloids. This customization allows more uniform illumination of one reflector by another. The BWG reflector shape is ellipsoidal. On the 70-m antennas, the subreflector directs received energy from the antenna onto a dichroic plate, a device which reflects S-band energy to the S-band feed horn and passes X-band energy through to the X-band feed horn. In the 34-m HEF, there is one 'common aperture feed,' which accepts both frequencies without requiring a dichroic plate. In the 34-m BWG, a series of small mirrors (approximately 2.5 meters in diameter) directs microwave energy from the subreflector region to a collection area at the base of the antenna -- typically in a pedestal room. A retractable dichroic reflector separates the S and X bands on some BWG antennas, or the X and Ka bands on others. RF energy to be transmitted into space by the horns is focused by the reflectors into narrow cylindrical beams, pointed with high precision (either to the dichroic plate or directly to the subreflector) by a series of drive motors and gear trains that can rotate the movable components and their support structures. The different antennas can be pointed by several means. Two pointing modes commonly used during tracking passes are CONSCAN and 'blind pointing.' With CONSCAN enabled and a closed-loop receiver locked to a spacecraft signal, the system tracks the radio source by conically scanning around its position in the sky. Pointing angle adjustments are computed from signal strength information (feedback) supplied by the receiver. In this mode the Antenna Pointing Assembly (APA) generates a circular scan pattern which is sent to the Antenna Control System (ACS). The ACS adds the scan pattern to the corrected pointing angle predicts. Software in the receiver-exciter controller computes the received signal level and sends it to the APA. The correlation of scan position with the received signal level variations allows the APA to compute offset changes which are sent to the ACS. Thus, within the capability of the closed-loop control system, the scan center is pointed precisely at the apparent direction of the spacecraft signal source. An additional function of the APA is to provide antenna position angles and residuals, antenna control mode/status information, and predict-correction parameters to the Area Routing Assembly (ARA) via the LAN, which then sends this information to JPL via the Ground Communications Facility (GCF) for antenna status monitoring. During periods when excessive signal level dynamics or low received signal levels are expected (e.g., during an occultation experiment), CONSCAN should not be used. Under these conditions, blind pointing (CONSCAN OFF) is used, and pointing angle adjustments are based on a predetermined Systematic Error Correction (SEC) model. Independent of CONSCAN state, subreflector motion in at least the z-axis may introduce phase variations into the received Radio Science data. For that reason, during certain experiments, the subreflector in the 70-m and 34-m HEFs may be frozen in the z-axis at a position (often based on elevation angle) selected to minimize phase change and signal degradation. This can be done via Operator Control Inputs (OCIs) from the NMC to the Subreflector Controller (SRC) which resides in the alidade room of the antennas. The SRC passes the commands to motors that drive the subreflector to the desired position. Pointing angles for all antenna types are computed by the NOCC Support System (NSS) from an ephemeris provided by the flight project. These predicts are received and archived by the CMC. Before each track, they are transferred to the APA, which transforms the direction cosines of the predicts into AZ-EL coordinates. The LMC operator then downloads the antenna predict points to the antenna-mounted ACS computer along with a selected SEC model. The pointing predicts consist of time-tagged AZ-EL points at selected time intervals along with polynomial coefficients for interpolation between points. The ACS automatically interpolates the predict points, corrects the pointing predicts for refraction and subreflector position, and adds the proper systematic error correction and any manually entered antenna offsets. The ACS then sends angular position commands for each axis at the rate of one per second. In the 70-m and 34-m HEF, rate commands are generated from the position commands at the servo controller and are subsequently used to steer the antenna. When not using binary predicts (the routine mode for spacecraft tracking), the antennas can be pointed using 'planetary' mode -- a simpler mode which uses right ascension (RA) and declination (DEC) values. These change very slowly with respect to the celestial frame. Values are provided to the station in text form for manual entry. The ACS quadratically interpolates among three RA and DEC points which are on one-day centers. A third pointing mode -- sidereal -- is available for tracking radio sources fixed with respect to the celestial frame. Also, at DSS 25, there is a special pointing mode to enable tracking at Ka-band frequency. Reception of the extremely narrow beamwidth Ka-band signals required the development of a monopulse receiver to continuously monitor and correct antenna pointing to maintain lock on the signal peak. And an aberration correction system had to be implemented such that the Ka-band uplink signal would be aimed at where the spacecraft would be when the signal arrived (simultaneously keeping the receiver pointed to where the downlink signal was when it left the spacecraft). This is accomplished by mounting the Ka-band transmit feed on a movable X-Y platform that can be displaced by as much as 30 millidegrees from the received beam. The monopulse tracking system (and Ka-band downlink) will be implemented at the other BWGs by the end of 2005. Regardless of the pointing mode being used, a 70-m antenna has a special high-accuracy pointing capability called 'precision' mode. A pointing control loop derives the main AZ-EL pointing servo drive error signals from a two- axis autocollimator mounted on the Intermediate Reference Structure. The autocollimator projects a light beam to a precision mirror mounted on the Master Equatorial drive system, a much smaller structure, independent of the main antenna, which is exactly positioned in HA and DEC with shaft encoders. The autocollimator detects elevation/cross- elevation errors between the two reference surfaces by measuring the angular displacement of the reflected light beam. This error is compensated for in the antenna servo by moving the antenna in the appropriate AZ-EL direction. Pointing accuracies of 0.004 degrees (15 arc seconds) are possible in 'precision' mode. The 'precision' mode is not available on 34-m antennas -- nor is it needed, since their beamwidths are twice as large as on the 70-m antennas. DSCC Antenna Microwave Subsystem -------------------------------- 70-m Antennas: Each 70-m antenna has three feed cones installed in a structure at the center of the main reflector. The feeds are positioned 120 degrees apart on a circle. Selection of the feed is made by rotation of the subreflector. A dichroic mirror assembly, half on the S-band cone and half on the X-band cone, permits simultaneous use of the S- and X-band frequencies. The third cone is devoted to R&D and more specialized work. The Antenna Microwave Subsystem (AMS) accepts the received S- and X-band signals at the feed horn and transmits them through polarizer plates to an orthomode transducer. The polarizer plates are adjusted so that the signals are directed to a pair of redundant amplifiers for each frequency, thus facilitating the simultaneous reception of signals in two orthogonal polarizations. For S-band these are two Block IVA S-band Traveling Wave Masers (TWMs); for X-band the amplifiers are Block IIA TWMs. 34-m HEF Antennas: The 34-m HEF uses a single feed for both S- and X-band. Simultaneous S- and X-band receive as well as X-band transmit is possible thanks to the presence of an S/X 'combiner' which acts as a diplexer. For S-band, RCP or LCP is user selected through a switch, so neither a polarizer nor an orthomode transducer is needed. The X-band amplification options include two Block II TWMs or a High Electron Mobility Transistor (HEMT) Low Noise Amplifier (LNA), while the S-band amplification is provided by a Field Effect Transistor (FET) LNA. 34-m BWG Antennas: These antennas use feeds and low-noise amplifiers (LNA) in the pedestal room, which can be switched in and out as needed. Typically the following modes are available: 1. downlink non-diplexed path (RCP or LCP) to LNA-1, with uplink in the opposite circular polarization; 2. downlink non-diplexed path (RCP or LCP) to LNA-2, with uplink in the opposite circular polarization; 3. downlink diplexed path (RCP or LCP) to LNA-1, with uplink in the same circular polarization; 4. downlink diplexed path (RCP or LCP) to LNA-2, with uplink in the same circular polarization. For BWG antennas with dual-band capabilities (e.g., DSS 25) and dual LNAs, each of the above four modes can be used in a single-frequency or dual-frequency configuration. Thus, for antennas with the most complete capabilities, there are sixteen possible ways to receive (2 polarizations, 2 waveguide path choices, 2 LNAs, and 2 bands). DSCC Receiver-Exciter Subsystem -- Pre-NSP ------------------------------------------ The Receiver-Exciter Subsystem is composed of three groups of equipment: the closed-loop receiver group (which includes the exciter equipment), the open-loop receiver group, and the RF monitor group. This subsystem is controlled by the Receiver- Exciter Controller (REC) which communicates directly with the DMC for predicts, and for OCI reception and status reporting. The exciter generates a sky-level signal which is provided to the Transmitter Subsystem for the spacecraft uplink signal. It is tunable under command of the DCO ( Digitally Controlled Oscillator), which receives uplink predicts from the Metric Data Assembly (MDA). The diplexer in the signal path between the transmitter and the feed horn for all antenna types (used for simultaneous transmission and reception) may be configured such that it is out of the received signal path (in listen-only or bypass mode) in order to improve the signal-to-noise ratio in the receiver system. Closed-Loop Receivers: The current closed-loop group consists of the Block V Receiver (BVR) and the Block V Exciter (BVE). The BVR allows for simultaneous use of two receiver channels, each configured independently of the other (thus allowing for the reception of two different frequencies/wavelengths/bands, or different polarizations of the same downlink band). Based on predicts from the MDA, the BVE provide a sky-level uplink signal to either the low-power or the high-power transmitter. The closed-loop receivers provide the capability for the rapid acquisition of a spacecraft signal, and telemetry lock-up. In order to accomplish signal acquisition within a short time, the receivers are predict driven to search for, acquire, and track the downlink automatically. Rapid acquisition precludes manual tuning, though that remains as a backup capability. The BVRs utilize FFT analyzers for rapid lock-up. The downlink predicts are generated by the NSS and then transmitted to the CMC, which sends them to the Receiver-Exciter Subsystem where two sets can be stored. The receiver starts acquisition at the beginning of a track (pass), or at an operator-specified time. The BVRs may also be operated from the NMC without local operators attending them. The receivers also send performance and status data, displays, and event messages to the NMC. With the BVRs, the simulation (SIM) synthesizer signal is used as the reference for the Doppler extractor. The synthesizer is adjusted before the beginning of the pass to a frequency that is appropriate for the channel (i.e., within the band) of the incoming signal; and will generally remain constant during the pass. The closed-loop receiver AGC loop can be configured to one of three settings: narrow, medium, or wide. It will be configured such that the expected amplitude changes are accommodated with minimum distortion. The loop bandwidth (2BLo) will be configured such that the expected phase changes can be accommodated while maintaining the best possible loop SNR. Open-Loop Receivers: The open-loop Radio Science Receiver (RSR) is a dedicated receiver that gets a downconverted signal (about 300 MHz), filters the signal to limit its bandwidth (to 265-375 MHz, centered at 320 MHz), and then further downconverts (to a center frequency of 64 MHz) and digitizes the signal. The RSR filters are specified by their bandwidths, desired resolution, and offset from the predicted sky frequency. The open-loop receivers operate in both a link-assigned and a stand-alone mode. In the link-assigned mode, the NMC receives monitor data from the RSR for incorporation into the data set for tracking support, and provides a workstation from which the RSR can be operated. RSRs that are not assigned to a link may be operated in a stand-alone mode without interference to any activities in progress at the complex. Monitor data is not sent to the NMC by RSRs operating in the stand-alone mode. DSCC Receiver-Exciter Subsystem -- Post-NSP ------------------------------------------- With the implementation of NSP, the receiver-exciter subsystem was split into the exciter component (called the UPL or Uplink Subsystem) and a separate receiver component (called the DTT or Downlink Tracking and Telemetry Subsystem). The UPL comprises the Exciter, the Command Modulation, the Uplink Controller, and the Uplink Ranging assemblies. The DTT comprises the Downlink Controller, the Receiver and Ranging Processor (RRP), and the Telemetry Processor (TLP) assemblies. The Post-NSP system is still based around the (Pre-NSP) Block V Exciter (BVE) and Block V Receiver (BVR) equipment. The output from the BVEs is uplink carrier and range phase, and the output from the BVRs is downlink carrier and range phase. The primary difference between the old and new systems is that these phase data (and not Doppler counts and ranging units) are what get delivered to the users. Furthermore, the UPL and DTT deliver these (phase) data directly to the Project, without passing it through any intervening system (that is, there is no longer an MDA or an SRA in the data flow path). Closed-Loop Receivers: Per the above, the closed-loop receiver is still based on the Block V receivers; but with NSP, it now has the capability to simultaneously support as many downlink channels as can be assigned by the NMC (up to a maximum of the total number of RRPs available at a given complex). The only other constraint is that any selected downlink band/bands must be supported by that antenna. Except that the MDA and SRA are now eliminated, the Pre-NSP and Post-NSP closed-loop receiver subsystems are basically the same. Open-Loop Receivers: The open-loop Radio Science Receiver (RSR) was unchanged by NSP, and its description is the same as that provided above in the Pre-NSP open-loop receiver description. DSCC Transmitter Subsystem -- Pre-NSP ------------------------------------- The Transmitter (TXR) Subsystem accepts a sky-level frequency exciter signal from the Receiver-Exciter Subsystem exciter. This signal is routed via the diplexer through the feed horn to the antenna, where it is then focused and beamed to the spacecraft. The Transmitter Subsystem power capabilities range from 18 kW to 400 kW, for S- and X-band uplink. Power levels above 18 kW are available only at 70-m stations. For Ka-band uplink (only at DSS 25), available powers range from 100 to 800 W. DSCC Transmitter Subsystem -- Post-NSP -------------------------------------- The Transmitter (TXR) Subsystem accepts a sky-level frequency exciter signal from the Uplink (Exciter) Subsystem exciter. This signal is routed via the diplexer through the feed horn to the antenna, where it is then focused and beamed to the spacecraft. The Transmitter Subsystem power capabilities range from 18 kW to 400 kW, for S- and X-band uplink. Power levels above 20 kW are available only at 70-m stations. For Ka-band uplink (only at DSS 25), available powers range from 100 to 800 W. DSCC Tracking Subsystem -- Pre-NSP ---------------------------------- The primary functions of the DSCC Tracking Subsystem (DTK) are to acquire and maintain communications with the spacecraft, and to generate and format radio metric data containing Doppler, range, and uplink frequencies (ramps). The DTK receives the carrier signals and ranging spectra from the Receiver-Exciter Subsystem. The Doppler cycle counts are computed from BVR-provided carrier phase measurements, and are then formatted and transmitted to JPL in real time. Ranging data are also formatted and transmitted to JPL in real time. Also contained in these blocks is the AGC information from the Receiver-Exciter Subsystem. The Radio Metric Data Conditioning Team (RMDCT) at JPL receives all of the DTK-generated tracking data and produces an Archival Tracking Data File (ATDF) which contains all of the Doppler, ranging, and ramp data. In addition, the Tracking Subsystem receives from the CMC frequency predicts (used to compute frequency residuals and noise estimates), receiver tuning predicts (used to tune the closed-loop receivers), and uplink tuning predicts (used to tune the exciter). From the NMC, it receives configuration and control directives, as well as configuration and status information on the transmitter, microwave, and frequency and timing subsystems. The Metric Data Assembly (MDA) controls all of the DTK functions supporting the uplink and downlink activities. The MDA receives uplink predicts, and controls the uplink tuning by commanding the DCO. The MDA also controls the Sequential Ranging Assembly (SRA). It formats the Doppler and ranging measurements, and the uplink frequency history (ramps), and provides them to the GCF for transmission to NOCC and RMDCT. The Sequential Ranging Assembly (SRA) measures the round trip light time (RTLT) of a radio signal traveling from a ground tracking station to a spacecraft and back. From the RTLT, phase, and Doppler data, the range to the spacecraft can be determined. A coded signal is modulated on an uplink carrier and transmitted to the spacecraft, where it is detected and transponded back to the ground station. As a result, the signal received at the tracking station is delayed by its round trip through space, and shifted in frequency by the Doppler effect due to the relative motion between the ground station on Earth and the spacecraft. DSCC Tracking Subsystem -- Post-NSP ----------------------------------- With NSP, all the Tracking Subsystem functions are incorporated within the Uplink Subsystem (UPL) and the Downlink Tracking and Telemetry Subsystem (DTT) -- the DTK, MDA, and SRA have now all been eliminated. DSCC Frequency and Timing Subsystem ----------------------------------- The Frequency and Timing Subsystem (FTS) provides all of the frequency and timing references required by the other DSCC subsystems. It contains four frequency standards, of which one is prime and the other three are backups. Selection of the prime standard is done via the CMC. Of these four standards, two are hydrogen masers followed by clean-up loops (CUL) and two are cesium standards. These four standards all feed the Coherent Reference Generator (CRG), which provides the frequency references used by the rest of the complex. It also provides the frequency reference to the Master Clock Assembly (MCA), which in turn provides time to the Time Insertion and Distribution Assembly (TID), which provides UTC and SIM-time to the complex. JPL's ability to monitor the FTS at each DSCC is limited to the station-calculated Doppler pseudo-residuals, the Doppler noise, the RSR, the SSI, and to a system that uses the Global Positioning System (GPS). GPS receivers at each DSCC receive a one-pulse-per-second signal from the station's (hydrogen- maser-referenced) FTS and a pulse from a GPS satellite at scheduled times. After compensating for the satellite signal delay, the timing offset is reported to JPL, where a database is kept. The clock offsets stored in the JPL database are given in microseconds; each entry is a mean reading of the measurements from several GPS satellites, and a time tag associated with the mean reading. The clock offsets that are provided include those of SPC 10 relative to UTC (NIST), SPC 40 relative to SPC 10, etc. Optics - DSN ============ Performance of the DSN ground stations depends primarily on size of the antenna and capabilities of the electronics. These are summarized in the following set of tables. Note that the 64-m antennas were upgraded to 70-m between 1986 and 1989. Beamwidth is half-power full angular width. Polarization is circular; L denotes left circular polarization (LCP), and R denotes right circular polarization (RCP). DSS S-Band Characteristics 70-m 34-m 34-m Transmit BWG HEF -------- ----- ----- ----- Frequency (MHz) 2110- 2025- N/A 2120 2120 Wavelength (m) 0.142 0.142 N/A Ant Gain (dBi) 62.7 56.1 N/A Beamwidth (deg) 0.119 N/A N/A Polarization L or R L or R N/A Tx Power (kW) 20-100 20 N/A Receive ------- Frequency (MHz) 2270- 2270- 2200- 2300 2300 2300 Wavelength (m) 0.131 0.131 0.131 Ant Gain (dBi) 63.3 56.7 56.0 Beamwidth (deg) 0.108 N/A 0.24 Polarization L & R L or R L or R System Temp (K) 20 31 38 DSS X-Band Characteristics 70-m 34-m 34-m Transmit BWG HEF -------- ----- ----- ----- Frequency (MHz) 8495 7145- 7145- 7190 7190 Wavelength (m) 0.035 0.042 0.042 Ant Gain (dBi) 74.2 66.9 67 Beamwidth (deg) N/A 0.074 Polarization L or R L or R L or R Tx Power (kW) 20 20 20 Receive ------- Frequency (MHz) 8400- 8400- 8400- 8500 8500 8500 Wavelength (m) 0.036 0.036 0.036 Ant Gain (dBi) 74.2 68.1 68.3 Beamwidth (deg) 0.031 N/A 0.063 Polarization L & R L & R L & R System Temp (K) 20 30 20 DSS Ka-Band Characteristics 70-m 34-m 34-m Transmit BWG HEF -------- ----- ----- ----- Frequency (GHz) N/A 34.2- N/A 34.7 Wavelength (m) N/A tbd* N/A Ant Gain (dBi) N/A tbd* N/A Beamwidth (deg) N/A tbd* N/A Polarization N/A L N/A Tx Power (W) N/A 800 N/A Receive ------- Frequency (GHz) N/A 31.8- N/A 32.3 Wavelength (m) N/A 0.009 N/A Ant Gain (dBi) N/A 77.9 N/A Beamwidth (deg) N/A 0.017 N/A Polarization N/A R N/A System Temp (K) N/A tbd* N/A NB: The X-band 70-m transmitting parameters are given at 8495 MHz, the frequency used by the Goldstone planetary radar system. For telecommunications, the transmitting frequency would be in the range 7145-7190 MHz, the power would typically be 20 kW, and the gain would be about 72.6 dB (70-m antenna). When ground transmitters are used in spacecraft radio science experiments, the details of transmitter and antenna performance rarely impact the results. Calibration - DSN ================= Calibrations of hardware systems are carried out periodically by DSN personnel; these ensure that systems operate at required performance levels -- for example, that antenna patterns, receiver gain, propagation delays, and Doppler uncertainties meet specifications. No information on specific calibration activities is available. Nominal performance specifications are shown in the tables above. Additional information may be available in [DSN810-5]. Prior to each tracking pass, station operators perform a series of calibrations to ensure that systems meet specifications for that operational period. Included in these calibrations is measurement of receiver system temperature in the configuration to be employed during the pass. Results of these calibrations are recorded in (hard copy) Controller's Logs for each pass. Operational Considerations - DSN ================================ The DSN is a complex and dynamic 'instrument.' Its performance for Radio Science depends on a number of factors from equipment configuration to meteorological conditions. No specific information on 'operational considerations' can be given here. Operational Modes - DSN ======================= DSCC Antenna Mechanical Subsystem --------------------------------- Pointing of DSCC antennas may be carried out in several ways. For details see the subsection 'DSCC Antenna Mechanical Subsystem' in the 'Subsystem' section. Binary pointing is the preferred mode for tracking spacecraft; pointing predicts are provided, and the antenna simply follows those. With CONSCAN, the antenna scans conically about the optimum pointing direction, using closed-loop receiver signal strength estimates as feedback. In planetary mode, the system interpolates from three (slowly changing) RA-DEC target coordinates; this is 'blind' pointing since there is no feedback from a detected signal. In sidereal mode, the antenna tracks a fixed point on the celestial sphere. In 'precision' mode, the antenna pointing is adjusted using an optical feedback system. At DSS 25 (only) there is also an 'aberration correction' mode that is needed whenever doing Ka-band uplink coherent downlink, because the transmit and receive beams must be pointed differently at the same time. In addition, it is possible on most antennas to freeze the z-axis motion of the subreflector to minimize phase changes in the received signal. DSCC Downlink Tracking and Telemetry Subsystem ---------------------------------------------- The diplexer in the signal path between the transmitter and the feed horns on all antennas may be configured so that it is out of the received signal path in order to improve the signal-to-noise ratio in the receiver system. This is known as the 'listen-only' or 'bypass' mode. Closed-Loop vs. Open-Loop Reception ----------------------------------- Radio Science data can be collected in two modes: closed- loop, in which a phase-locked loop receiver tracks the spacecraft signal, or open-loop, in which a receiver samples and records a band within which the desired signal presumably resides. Closed-loop data are collected using Closed-Loop Receivers, and open-loop data are collected using Open-Loop Receivers in conjunction with the Full Spectrum Processing Subsystem (FSP). See the Subsystems section for further information. Closed-Loop Receiver AGC Loop ----------------------------- The closed-loop receiver AGC loop can be configured to one of three settings: narrow, medium, or wide. In general, it is configured so that expected signal amplitude changes are accommodated with minimum distortion. The loop bandwidth is typically configured so that expected phase changes can be accommodated while maintaining the best possible loop SNR. Coherent vs. Non-Coherent Operation ----------------------------------- The frequency of the signal transmitted from the spacecraft can generally be controlled in two ways -- by locking to a signal received from a ground station or by locking to an on-board oscillator. These are known as the coherent (or 'two-way') and non-coherent ('one-way') modes, respectively. Mode selection is made at the spacecraft, based on commands received from the ground. When operating in the coherent mode, the transponder carrier frequency is derived from the received uplink carrier frequency with a 'turn-around ratio' as expressed in the table below: Uplink Downlink Turn-Around Band Band Ratio --------------------------------- X X 880/749 X S 240/749 X Ka 3344/749 Ka Ka 14/15 In the non-coherent mode, the downlink carrier frequency is derived from the spacecraft's on-board, crystal-controlled oscillator. Either closed-loop or open-loop receivers (or both) can be used with either spacecraft frequency reference mode. Closed-loop reception in the two-way mode is usually preferred for routine tracking/navigation. Occasionally the spacecraft operates coherently such that one ground station does the transmitting, and a second/different ground station receives the 'downlink' signal -- this is referred to as the 'three-way' mode. Media Calibration System ------------------------ The Earth's atmosphere contributes phase and amplitude noise to the spacecraft radio signal received at a ground station. Each DSCC has a GPS receiver subsystem to calibrate for both the ionosphere and troposphere (both wet and dry components), along the zenith direction. This subsystem also measures the temperature, pressure, humidity, wind speed and direction, and Faraday rotation. Radio Science experiments that utilize Ka-band downlink, where excellent end-to-end frequency and phase stability are required, necessitated the development of a new system to calibrate the effects of the atmosphere on the phase of the microwave signal. The purpose of this new media calibration system is to provide a line-of-sight measurement of water vapor delay (responsible for the majority of the atmosphere-induced phase fluctuations at microwave frequencies). It also provides estimates of total zenith delay and delay fluctuation. This is accomplished via: (1) an advanced water vapor radiometer to sense the number of water vapor molecules along the line-of-sight; (2) a microwave temperature profiler to sense vertical temperature distribution; (3) a surface meteorology package to measure the temperature, pressure, and humidity; and (4) a GPS receiver to provide the total zenith delay estimates. This 'advanced' system is only implemented at DSS 25 at this time. Location - DSN ============== Accurate spacecraft navigation using radio metric data requires knowledge of the locations of the DSN tracking stations. The coordinate system in which the locations of the tracking stations are expressed should be consistent with the reference frame definitions used to provide Earth orientation calibrations. The International Earth Rotation Service (IERS) has established a terrestrial reference frame for use with Earth orientation measurements. The IERS issues a new realization of the terrestrial reference frame each year. The definition of the coordinate system has been changing slowly as the data have been improved, and as ideas about how to best define the coordinate system have developed. The overall changes from year to year have been at the few-cm level. The 1993 version of the IERS Terrestrial Reference Frame (ITRF1993) [BOUCHERETAL1994] is most used for DSN station locations. The DSN station locations have been determined by use of VLBI measurements, and by conventional and GPS surveying. Tables of station locations are available in either Cartesian or geodetic coordinates. The geodetic coordinates are referred to a geoid with an equatorial radius of 6378136.3 m, and a flattening factor f=298.257, as described in IERS Technical Note 13. The DSN Station Locations in ITRF1993 Cartesian reference frame at epoch 1993.0 (assuming subreflector-fixed configuration) are as follows: Antenna x(m) y(m) z(m) ------------------------------------------------ DSS 12 -2350443.812 -4651980.837 +3665630.988 DSS 13 -2351112.491 -4655530.714 +3660912.787 DSS 14 -2353621.251 -4641341.542 +3677052.370 DSS 15 -2353538.790 -4641649.507 +3676670.043 DSS 16 -2354763.158 -4646787.462 +3669387.069 DSS 17 -2354730.357 -4646751.776 +3669440.659 DSS 23 -2354757.567 -4646934.675 +3669207.824 DSS 24 -2354906.528 -4646840.114 +3669242.295 DSS 25 -2355021.795 -4646953.325 +3669040.628 DSS 26 -2354890.967 -4647166.925 +3668872.212 DSS 27 -2349915.260 -4656756.484 +3660096.529 DSS 28 -2350101.849 -4656673.447 +3660103.577 DSS 33 -4461083.514 +2682281.745 -3674570.392 DSS 34 -4461146.720 +2682439.296 -3674393.517 DSS 42 -4460981.016 +2682413.525 -3674582.072 DSS 43 -4460894.585 +2682361.554 -3674748.580 DSS 45 -4460935.250 +2682765.710 -3674381.402 DSS 46 -4460828.619 +2682129.556 -3674975.508 Parkes -4554231.843 +2816758.983 -3454036.065 DSS 53 +4849330.129 -0360338.092 +4114758.766 DSS 54 +4849434.496 -0360724.062 +4114618.570 DSS 55 +4849525.318 -0360606.299 +4114494.905 DSS 61 +4849245.211 -0360278.166 +4114884.445 DSS 63 +4849092.647 -0360180.569 +4115109.113 DSS 65 +4849336.730 -0360488.859 +4114748.775 DSS 66 +4849148.543 -0360474.842 +4114995.021 The DSN Station Locations in ITRF1993 Geodetic reference frame at epoch 1993.0 (assuming subreflector-fixed configuration) are as follows: latitude longitude height Antenna deg min sec deg min sec (m) ---------------------------------------------------------- DSS 12 35 17 59.77577 243 11 40.24697 962.87517 DSS 13 35 14 49.79342 243 12 19.95493 1071.17855 DSS 14 35 25 33.24518 243 6 37.66967 1002.11430 DSS 15 35 25 18.67390 243 6 46.10495 973.94523 DSS 16 35 20 29.54391 243 7 34.86823 944.71108 DSS 17 35 20 31.83778 243 7 35.38803 937.65000 DSS 23 35 20 22.38335 243 7 37.70043 946.08556 DSS 24 35 20 23.61492 243 7 30.74701 952.14515 DSS 25 35 20 15.40494 243 7 28.70236 960.38138 DSS 26 35 20 8.48213 243 7 37.14557 970.15911 DSS 27 35 14 17.78052 243 13 24.06569 1053.20312 DSS 28 35 14 17.78136 243 13 15.99911 1065.38171 DSS 33 -35 24 1.76138 148 58 59.12204 684.83864 DSS 34 -35 23 54.53984 148 58 55.06236 692.71119 DSS 42 -35 24 2.44494 148 58 52.55396 675.35557 DSS 43 -35 24 8.74388 148 58 52.55394 689.60780 DSS 45 -35 23 54.46400 148 58 39.65992 675.08630 DSS 46 -35 24 18.05462 148 58 59.08571 677.55141 Parkes -32 59 54.25297 148 15 48.64683 415.52885 DSS 53 40 25 38.48036 355 45 1.24307 827.50081 DSS 54 40 25 32.23152 355 44 45.24459 837.60097 DSS 55 40 25 27.45965 355 44 50.51161 819.70966 DSS 61 40 25 43.45508 355 45 3.51113 841.15897 DSS 63 40 25 52.34908 355 45 7.16030 865.54412 DSS 65 40 25 37.86055 355 44 54.88622 834.53926 DSS 66 40 25 47.90367 355 44 54.88739 850.58213 Measurement Parameters - DSN ============================ Open-Loop System ---------------- Output from the Open-Loop Receivers (OLRs), as sampled and recorded by the Radio Science Receiver (RSR), is a stream of 1-, 2-, 4-, 8-, or 16-bit I (In-Phase) and Q (Quadrature-Phase) samples. The spacecraft transmits an RF signal to an antenna, where the signal gets downconverted to IF. The RSR selects an IF signal for a particular frequency band and passes it through a digitizer (where it is attenuated and then mixed with timing information). The signal is then decimated, filtered (to I&Q samples), and then multiplied by the signal from a numerically controlled oscillator. Finally, the RSR reduces the bandwidth and sample rate of the samples, and truncates the results (thus creating an offset of -0.5 in the output data). The samples of data are packed into SFDU blocks (nominally containing a single second's worth of data), and a header is attached to provide the following associated data for the record: - time tag for the first sample in the data block - data source identification (DSS, RSR, and sub-channel), and frequency band - data sample resolution (bits per sample) and rate (samples per second) - filter gain, ADC RMS amplitude, and attenuation - frequency and phase polynomial coefficients Closed-Loop System ------------------ Prior to mid 2003, closed-loop data were recorded in Archival Tracking Data Files (ATDFs), as well as certain higher-level products such as Orbit Data Files (ODFs). After May 2003 these data were provided in Tracking and Navigation Files (TNFs). During NSP implementation (January through May 2003), there was a transition from ATDFs to TNFs as the ground stations switched to the new DSN tracking system, one at a time. The ATDFs and the ODFs contained fixed-length, fixed-format, bit-oriented, binary integer data records; the TNFs, on the other hand, are comprised of SFDUs that have variable-length, variable-format records with mixed typing (i.e., can contain ASCII, integer, and floating-point items in a single record). These files all contain entries that include measurements of Doppler, range, and signal strength, along with status and uplink frequency information. ACRONYMS AND ABBREVIATIONS - DSN ================================ ACS Antenna Control System ADC Analog-to-Digital Converter AGC Automatic Gain Control AMMOS Advanced Multi-Mission Operations System AMS Antenna Microwave System APA Antenna Pointing Assembly ARA Area Routing Assembly ATDF Archival Tracking Data File AUX Auxiliary AZ Azimuth BPF Band Pass Filter bps bits per second BVE Block V Exciter BVR Block V Exciter BWG Beam WaveGuide (antenna) CAS Cassini CCT Central Communications Terminal CDU Command Detector Unit CMC Complex Monitor and Control CONSCAN Conical Scanning (antenna pointing mode) CRG Coherent Reference Generator CSO Compensated Sapphire Oscillator CUL Clean-up Loop DANA a type of frequency synthesizer dB deciBel dBi dB relative to isotropic dBm dB relative to one milliwatt DCO Digitally Controlled Oscillator DEC Declination deg degree DMC DSCC Monitor and Control Subsystem DOD Differential One-Way Doppler DOR Differential One-way Ranging DSCC Deep Space Communications Complex DSN Deep Space Network DSS Deep Space Station DST Deep Space Transponder DTK DSCC Tracking Subsystem DTT DSCC Downlink Tracking and Telemetry Subsystem E east EIRP Effective Isotropic Radiated Power EL Elevation FET Field Effect Transistor FFT Fast Fourier Transform FSP Full Spectrum Processor Subsystem FTS Frequency and Timing Subsystem GCF Ground Communications Facility GHz Gigahertz GPS Global Positioning System GSFC Goddard Space Flight Center HA Hour Angle HEF High-Efficiency (as in 34-m HEF antennas) HEMT High Electron Mobility Transistor (amplifier) HGA High-Gain Antenna HSB High-Speed BWG I In-phase IERS International Earth Rotation Service IF Intermediate Frequency IVC IF Selection Switch JPL Jet Propulsion Laboratory K Kelvin Ka-Band approximately 32 GHz KAT Ka-Band Translator kbps kilobits per second KEX Ka-Band Exciter kHz kilohertz km kilometer kW kilowatt LAN Local Area Network LCP Left-Circularly Polarized LGA Low-Gain Antenna LMC Link Monitor and Control LNA Low-Noise Amplifier LO Local Oscillator m meters MCA Master Clock Assembly MDA Metric Data Assembly MHz Megahertz MON Monitor and Control System MSA Mission Support Area N north NAR Noise Adding Radiometer NBOC Narrow-Band Occultation Converter NIST SPC 10 time relative to UTC NIU Network Interface Unit NMC Network Monitor and Control NOCC Network Operations and Control System NRV NOCC Radio Science/VLBI Display Subsystem NSP Network Simplification Project NSS NOCC Support Subsystem OCI Operator Control Input ODF Orbit Data File ODR Original Data Record OLR Open-Loop Receiver OSC Oscillator PDS Planetary Data System PPM Precision Power Monitor Q Quadrature RA Right Ascension REC Receiver-Exciter Controller RCP Right-Circularly Polarized RF Radio Frequency RFE (Probe) Receiver Front End RFIS Radio Frequency Instrument Subsystem RFS Radio Frequency Subsystem RMDCT Radio Metric Data Conditioning Team RMS Root Mean Square RNS Reliable Network Server RRP Receiver and Ranging Processor RSR Radio Science Receiver RSS Radio Science Subsystem RSSG Radio Science Systems Group RTLT Round-Trip Light Time S-band approximately 2100-2300 MHz SBT S-Band Transmitter sec second SEC Systematic Error Correction SFDU Standard Format Data Unit SIM Simulation SLE Signal Level Estimator SNR Signal-to-Noise Ratio SNT System Noise Temperature SOE Sequence of Events SPA Spectrum Processing Assembly SPC Signal Processing Center sps samples per second SRA Sequential Ranging Assembly SRC Sub-Reflector Controller SSI Spectral Signal Indicator tbd to be determined TDDS Tracking Data Delivery Subsystem TID Time Insertion and Distribution Assembly TLM Telemetry TLP Telemetry Processor TSF Tracking Synthesizer Frequency TWM Traveling Wave Maser TWNC Two-Way Non-Coherent TWTA Traveling Wave Tube Amplifier TXR Transmitter (subsystem) UNK unknown UPL DSCC Uplink Subsystem USO UltraStable Oscillator UTC Universal Coordinated Time VCO Voltage-Controlled Oscillator VF Video Frequency VLBI Very Long Baseline Interferometry X-band approximately 7800-8500 MHz