File perf-interface.spe, version 1.5, released 95/11/21 at 09:57:05. 951121 LRD Change "WE" to give rel humidity rather than dew point. 951006 LRD Revised based on comments received. 950525 LRD Revised based on comments received. Added satellite-dependent formats for VSOP. 950217 LRD Original issue, draft for review. NATIONAL RADIO ASTRONOMY OBSERVATORY Green Bank, West Virginia SPECIFICATION: A34300N0008C DATE: 21 November 1995 TITLE: Spacecraft/Station Performance Log Interface PREPARED BY: L. D'Addario APPROVED BY___________________ 1.0 GENERAL This specification describes an output file from the Green Bank Earth Station, and possibly from other OVLBI earth stations. It is created after the end of a satellite tracking pass by processing the real-time log file created during the pass. It is intended for use by other mission elements to determine how well the spacecraft and earth station performed. The general concepts of log file generation are given in NRAO Specification A34300N006A, and the transfer of all interface files between mission elements is covered by Specification A34300N001. 2.0 LOGICAL CONTENT The following information will be reported in this file: 2.1 Acquisition parameters: When stable downlink signals are first acquired during a pass, or re-acquired after a dropout, the ground time, tape time, and assumed downlink delay at the clock setting epoch are reported. 2.2 Downlink signal flux density estimate: The earth station's best estimate of the received flux density on each active downlink, in W/m^2, is reported periodically after signal acquisition. 2.3 Timing link statistics: For each 5-minute interval, the least-squares fit of a straight line to the residual two-way delay is computed; the initial delay, slope (average Doppler), and rms deviation of the fit are reported. 2.4 Anomalies: All anomalous conditions detected by the real time software are reported except those that are only at the "warning" level. Downlink header data as well as earth station monitor data are checked for anomalies. A record is made in this file whenever the error level of a given condition CHANGES. 2.5 Satellite state: Satellite payload status bits are reported after initial signal acquisition and whenever they change, regardless of whether they indicate an anomaly. 2.6 Wideband data quality statistics: The following counters are reset to zero after initial signal acquisition; the (cumulative) content of each is reported every 5 minutes thereafter: 2.6.1 Frames processed - number of downlink frames written to tape (whether valid or not) 2.6.2 Syncs missed - number of times sync word was not detected at the expected time 2.6.3 Re-syncs - number of times sync word was detected at other than the expected time, forcing a re-synchronization 2.6.4 Invalid frames - number of downlink frames replaced by pseudo-random noise on the tape. For VSOP, normally equal to "re-syncs"; but for Radioastron an invalid frame also occurs if the number of parity errors is excessive. 2.7 Downlink header quality statistics: Similar to 2.6, a set of error counters is maintained when processing the downlink header data. These are different for VSOP and Radioastron; details are given in Appendices A and B. The counters are set to zero after initial acquisition and their cumulative contents are reported every 5 minutes thereafter. 2.8 Weather: Ambient temperature, humidity, and pressure at the earth station antenna are reported at intervals of 10 minutes. 2.9 Major events: Important events will be reported, including 2.9.1 Turning uplink transmitter on or off, with power setting 2.9.2 Starting a new tape, with tape serial number 2.9.3 Manual intervention by an operator 2.10 Operator notes: Messages entered by the operator. 2.11 Other: Additional record types might be defined later. 3.0 FILE FORMAT The file contains only standard ASCII characters (7 bits), with each record terminated by . If any record contains the '#' character, then that character and everything following it in the same record is a comment for humans; comments should be ignored by machines. Except for comments, each record consists of a sequence of FIELDS delimited by any number of or characters. Each field is either a decimal number in "g-format" (with optional decimal point and optional exponent subfield) or a character string enclosed in double-quote (") characters. The length of each field is variable, being whatever is required to represent the value with adequate precision. Each record contains the following fields: 3.1 DATE: Day of year, where January 1 is day 1. 3.2 TIME: UTC as six digits in the form HHMMSS. 3.3 STATION: Code for station generating this record, following conventions established elsewhere (5 character quoted string). 3.4 RECORD TYPE: Code specifying the meaning of the remainder of this record (2 character quoted string). The code for each of the record types specified in section 2 above is given in 3.5 below. 3.5 DATA: One or more fields specific to the record type, as follows. NAME TYPE DATA 3.5.1 Acquisition "AC" 3.5.2 Downlink flux "DF" 3.5.3 Timing link "TL" 3.5.4 Anomalies "AN" "" 3.5.5 Satellite state "SS" ... [see 2.5] 3.5.6 Wideband data "WD" \ 3.5.7 Header quality "HQ" ... [see 2.7] 3.5.8 Weather "WE" 3.5.8 Uplink transmit "UL" 3.5.9 New Tape "NT" 3.5.10 Manual control "MC" "" 3.5.11 Operator notes "OP" "" Some or all of the data fields may be omitted, indicating that the corresponding information is not available, but allowing the remaining information in the record to be recorded. A record may be terminated at any point to indicate omission of all remaining fields; to omit a field while including later fields, the omitted field must be replaced by an empty pair of double quotes (""), even if the field is normally numeric. Whenever a data field is a dimensioned quantity, the rationalized MKS system of units will be used, as shown above. 3.6 The (3.5.1) is a one-character identifier, "R" for Radioastron, "V" for VSOP, "S" for SURFSAT. All time intervals are in seconds, and times of day are in seconds past midnight. 3.7 The satellite state data (2.5 and 3.5.5) and header quality counters (2.7 and 3.5.7) are satellite dependent. Details are given in Appendices A and B for VSOP and Radioastron, respectively. 3.8 The parameter in the Anomalies record can have the following values: 0 - No error. 1 - Warning (will not occur in this file). 2 - Error. This means that the condition is significant enough that some or all of the station output data is likely to be bad, including either the signal recorded on the wideband tape or the two-way delay residuals or both. 3 - Severe. Some or all output data is certainly bad, and normal operation cannot continue. 4 - Emergency. The condition is so severe that the station has entered its automatic shutdown mode; operation has been discontinued. (Examples include power failure and very high wind.) 4.0 EXAMPLE The following lines represent a short segment of a file conforming to this specification. 212 152008 "GBANK" "AC" "R" 55206.73102352 55207 5.731e-2 212 152500 "GBANK" "DF" 15.1 2.51e-13 212 152500 "GBANK" "DF" 8.47 3.14e-14 212 152500 "GBANK" "WE" 27.0 0.35 91730 These records indicate that on day 212 (July 31) at 15:20:08, acquisition of Radioastron had occurred, causing the tape clock to be set to 55207 sec UTC (15:20:07) at station time 55206.73102352 sec. About 5 min later, the estimated received flux was 0.251 pW/m^2 on the 15.1 GHz link, and .0314 pW/m^2 on the 8.47 GHz link; the temperature at Green Bank was 27.0 C, relative humidity was 0.35 (35%), and pressure was 917.30 mb. APPENDIX A: SATELLITE DEPENDENT DATA, VSOP A.1 The satellite state, record type "SS", consists of a list of the values of selected bytes of header data, reported just after initial acquisition and again whenever any of the values changes. A total of 9 bytes of data will be reported, each as an unsigned integer between 0 and 255, in the following order, where x:y represents ID=x, word=y in the downlink header format described in [1]. 3:8 - link status (also 7:8, 11:8, 15:8); 12:6, 12:7 - various on/off bits and IF switch positions; 13:6 - noise diode status; 13:7 - SSF status; 14:6, 14:7 - synthesizer A status; 15:6, 15:7 - synthesizer B status. A.2 The header quality statistics, record type "HQ", consists of the contents of 8 counters whose cumulative values are reported as unsigned integers in the following order. The respective counters are initialized to zero and incremented when: A.2.1 A header is discarded because its frame was out of sync; A.2.2 A header is discarded because its repeat count (W4) was invalid; A.2.3 A block is discarded because its ID bytes (W5) were inconsistent; A.2.4 An information byte is discarded because there was not enough agreement among the 25 frames in which it was repeated; A.2.5 A short block (<25 frames) is received; A.2.6 A long block (>25 frames) is received; A.2.7 A short group (<16 IDs) is received; A.2.8 A long group (>16 IDs) is received. It should be noted that occasional short groups and long groups are normal, but all other counts represent errors. Further details of the processing needed to determine these values are given in [2]. APPENDIX B: SATELLITE DEPENDENT DATA, RADIOASTRON (To be added in a later revision of this specification.) REFERENCES [1] ISAS, "Muses-B Ku-band telemetry format." Document VSOP-5130, revision 4, dated June 30, 1993. [2] L. D'Addario, "VSOP Header Processing Design Document." NRAO internal document, last revised 94/12/02. Available via anonymous ftp from ftp.gb.nrao.edu:ovlbi/doc/vsopHeaderProc.doc.