NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

STARDUST 9P/TEMPEL 1 DFMI 2/3 NEXT V1.0 (PDS)

NSSDCA ID: PSSB-00549

Availability: Archived at NSSDC, accessible from elsewhere

Time span: 2007-01-25 to 2011-03-01

Description

This description was generated automatically using input from the Planetary Data System.

Data Set Overview

This description was written by B. Carcich with support from the Stardust-NExT operations and science teams.

This data set contains Level 2 (EDR) and 3 (RDR) data collected by the Dust Flux Monitor Instrument (DFMI) during the Stardust-NExT mission from January, 2007, through cruise, approach to and encounter with comet 9P/Tempel 1, and up to end of mission in March, 2011. The Tempel 1 encounter data span a ~40 minute period. The RDR data convert the EDR (raw) sensor data, from the entire comet encounter, to dust fluences at each of twelve mass thresholds. These data record dust impact and other events which resulted from interstellar particles, the encounter with particles surrounding Tempel 1, instrument commands such as automated calibrations, and an instrument anomaly, which generated false positive events, that was known to occur after the DFMI has been powered on for over thirty minutes. Data Collection Periods ======================= The only DFMI science data were taken at encounter with 9P/Tempel 1. Throughout the Stardust-NExT mission the DFMI was powered on infrequently because of the power supply anomaly that typically occurred when it was on for longer than about thirty minutes. Except for the ENCOUNTER period, the DFMI was mainly turned on two minutes at a time for calibration and checkout to assess instrument health. The forty-nine minutes of operation on 2008-12-10 was a checkout exercise to determine if the anomaly was still an issue; the anomaly appeared less than nineteen minutes after power-on. At encounter, the anomaly appeared at about 2011-02-15T04:44:00, twenty-seven minutes after power on and five minutes after closest approach; data after that point are suspect as science data. The periods when the DFMI was powered on, as well as the model and the times when the anomaly started, if present, are as follows: Mode: CRUISE Start: 2007-01-25T20:37:37.997 Anomaly: N/A Stop: 2007-01-25T20:39:20.294 Duration: ~2 minutes Mode: CRUISE Start: 2008-12-10T18:48:03.661 Anomaly: 2008-12-10T19:06:45.462 Stop: 2008-12-10T19:36:49.184 Duration: ~49 minutes Mode: CRUISE Start: 2010-06-29T15:48:49.910 Anomaly: N/A Stop: 2010-06-29T15:50:32.210 Duration: ~2 minutes Mode: CRUISE Start: 2011-02-02T17:12:08.805 Anomaly: N/A Stop: 2011-02-02T17:13:51.106 Duration: ~2 minutes Mode: ENCOUNTER Start: 2011-02-15T04:17:16.415 Anomaly: 2011-02-15T04:44:28.003 Stop: 2011-02-15T04:57:12.315 Duration: ~40 minutes Mode: CRUISE Start: 2011-03-01T22:10:53.654 Anomaly: 2011-03-01T22:42:50.531 Stop: 2011-03-01T23:00:53.542 Duration: ~50 minutes Data Calibration ================ This data set contains one PDS TABLE of calibrated data for the encounter with comet 9P/Tempel 1. The table lists fluence, mass threshold and uncertainties for each of the DFMI threshold circuits. There are no calibrated data corresponding to the non-ENCOUNTER CRUISE mode raw data. Calibration sources ------------------The calibrations for this instrument were derived from laboratory and pre-launch testing. The stability of the instrument was monitored in-flight by injecting a known signal to the electronics and monitoring the digital counters. Calibration process ------------------This data set includes documents (see /DOCUMENT/DOCINFO.TXT) along with references to published papers detailing the calibration of the two types of sensors in DFMI. A summary of the calibration process follows. There are several aspects to DFMI calibration. One aspect is converting raw counter data, which incremented between time samples, into a number of impacts. This is roughly a straightforward one-for-one operation for the PVDF sensors, with a possible correction for counter overflow. However, it is more complex for the acoustic sensors, where the counters indicate the fraction of time decaying oscillating signals, each generated by a single impact, exceeded each of two different threshold voltages. Another issue is that the incremental counts over two or more contiguous time periods may need to be combined to properly understand the data. This data set includes a spreadsheet where this accounting is performed and a document where the process is explained. See /DOCUMENT/AC/AC.LBL, especially AC_PROCESS.* and AC_T1_CT2IMP*.*. A second aspect is determining the mass threshold, with uncertainties, that applies to each of the threshold circuits. For the PVDF sensors this involved scaling ground-based laboratory data to the Tempel 1 encounter speed (10.9km/s); see [ECONOMOUETAL2011] for details. For the acoustic sensor, see /DOCUMENT/AC/AC.LBL, especially AC_PROCESS.*. A third aspect is calculating fluence (impacts m^-2). Again this is fairly straightforward for the PVDF sensor: divide the number of impacts for each threshold by the area of the corresponding PVDF sensor (0.02m^2 or 0.002m^2). For the acoustic sensor the fluence calculation is complicated by the large extent of the shield which means the impact of a small particle near the piezoelectric sensors cannot be distinguished from that of a larger particle farther away. This can be resolved if the mass distribution of the impacting particle population is known, so a distribution is assumed to calculate the fluences. The resulting fluences are then checked against the assumed distribution to see if they are consistent, and if not then these steps are repeated until the process converges. This approach is implemented via a correlation between a 'mass distribution index' and an 'effective' area of the acoustic surface that is a function of that index. The index is the exponent of a power law distribution; see /DOCUMENT/AC/AC.LBL, especially AC_DFMI.*, as well as [TUZZOLINOETAL2003], [GREENETAL2004] and [ECONOMOUETAL2011]. Data Product Type and Format Overview ===================================== DFMI data files provided in this archive are divided into two main categories: raw (EDR); calibrated (RDR). The raw data are further divided by target, INTERSTELLAR PARTICLES and 9P/TEMPEL 1 (1867 G1), which also corresponds to DFMI mode, CRUISE and ENCOUNTER, respectively. Two further types of ancillary data have been provided at the request of the peer reviewers to aid in interpreting the 9P/Tempel encounter flyby DFMI events: 1) The PVDF data are 'unrolled' to remove the effect of counter rollover, where the recorded raw value decreased (reset to zero) as event counts increased, although no rollover occurred as a result of dust impact events i.e. all PVDF rollovers occurred only after the power supply anomaly began to cause false positive impact events. The count rates have also been calculated in the data product containing these unrolled counts. 2) Thruster firing events during the encounter flyby with 9P/Tempel 1 have been supplied to allow assessment of the possibility that thruster activity could have caused false positive impact events. The data files provide data as ASCII-formatted comma-separated-values (CSVs). In the EDR data, each row represents a single sample in time. In the RDR data, each row represents an accumulated fluence for the duration of the Tempel 1 encounter for one threshold. There are no RDR data corresponding to the non-ENCOUNTER CRUISE mode EDR data. Refer to the data labels (*.LBL) for the meaning of each CSV in a row. See 'Parameters - Sampling interval' below for details of what times may be represented in each EDR row. Parameters ========== Each parameter is stored as one ASCII CSV in a row. Refer to the data labels (*.LBL) for the format and location of the data file parameters. EDR data -------EDR data contain the time-cumulative raw counter values with rollover. As noted above, for PVDF sensors these counters are roughly 1:1 with actual impacts, and for acoustic sensors the relationship is more complicated. The PVDF sensor counters are 16-bit and roll over (reset to zero) after 65,535 counts; the acoustic sensors roll over after 255 counts. The PVDF counters are also threshold-cumulative i.e. each nominal impact is only counted once in one of the threshold counters and an impact detected and counted by one of the higher thresholds does not register as an impact in any lower threshold. EDR data also contain synoptic data at each time the counters are read. The synoptic data include UTC time at the spacecraft, DFMI configuration, DFMI temperatures, a sync byte, spacecraft position and velocity relative to some or all of Earth, Sun, and comet 9P/Tempel 1. Refer to the EDR data labels for further detail. RDR Data -------The calibrated data for the ENCOUNTER contain the particle mass corresponding to each voltage threshold, an equivalent spherical particle diameter, the fluence of the particles above each threshold, and uncertainties for mass and fluence. There are no RDR data corresponding to the non-ENCOUNTER CRUISE mode EDR data. Sampling Intervals -----------------In CRUISE mode, the DFMI updates counter values up to ten times per second, but only when some of the counters change. ENCOUNTER mode is almost identical, except that updates are sent at least once per second even if no changes occur. EDR data contain data sampled at these intervals. RDR ENCOUNTER data contain fluences (cumulative impacts) for the duration of the encounter up to before the start of the anomaly. There are no RDR data corresponding to the non-ENCOUNTER CRUISE mode EDR data. Thruster firings ---------------The thruster firing data have been extracted from a Small Forces File, available from JPL/NAIF (http://naif.jpl.nasa.gov/) and as described in the Stardust Wild 2 Encounter Dynamic Science Experiment Data set [SEMENOVETAL2004C]. Data Processing =============== The Stardust DFMI instrument output consisted of a variety of binary data blocks. On board the spacecraft these blocks were packetized by the spacecraft's flight software and downlinked within packets in the spacecraft telemetry stream. A suite of software -- developed and run by the Stardust Data Management and Archive Team (DMA) -- retrieved packets with DFMI data from the Telemetry Data Server(s)(TDS) used by the Stardust Project, stripped off ground system and spacecraft packet headers, and placed the binary data in a binary collection file. For readability, the binary data were also converted to ASCII text, combined with ancillary information such as spacecraft, comet, Sun and Earth relative positions, and stored as comma-separated values (CSVs) in the EDR data files in this archive. The ENCOUNTER RDR data were extracted from the last of a series of calibration spreadsheet workbooks, which are archived with this data set in the /DOCUMENT/ directory. Ancillary Data ============== Each data file includes a number of derived geometry parameters. These parameters were computed using the following SPICE kernels archived in the Stardust SPICE data set, SDU-C-SPICE-6-V1.0: Kernel Type File Name ------------ -----------------------LSK naif0009.tls PCK pck00009.tpc SCLK sdu_sclkscet_00186.tsc FK sdu_v20.tf SPKs sdu_tempel1_ssd_s154.bsp' sdu_isp000.bsp' sdu_l_1999.bsp' sdu_l_2000.bsp' sdu_l_2001.bsp' sdu_l_2002.bsp' sdu_l_2003_w2.bsp' sdu_l_2004.bsp' sdu_l_2005_return.bsp' sdu_l_2006.bsp' sdu_l_2007.bsp' sdu_l_2008.bsp' sdu_l_2009.bsp' sdu_l_2010.bsp' sdu_l_2011_t1.bsp' CKs sdu_sc_rec_1999_v2.bc sdu_sc_rec_2000_v2.bc sdu_sc_rec_2001_v2.bc sdu_sc_rec_2002_v2.bc sdu_sc_rec_2003_w2_v2.bc sdu_sc_rec_w2_opnav.bc sdu_sc_rec_2004_v2.bc' sdu_sc_rec_2005_v2.bc' sdu_sc_rec_next.bc' ------------ -----------------------Coordinate System ================= The geometry items provided in the files are relative to the J2000 reference frame. Refer to the specification of the geometry table columns to see which parameters are defined in which frame. The J2000 reference frame is defined as follows: - +Z axis is along Earth Mean Equator North at the J2000 epoch (2000 JAN 01 12:00 ET); - +X axis is along the vernal Equinox at the J2000 epoch; - +Y completes the right hand frame; The Stardust reference frame is defined as follows: - +X axis is along the longer side of the spacecraft bus and points from the aerogel capsule side towards the dust shield side; - +Z is perpendicular to the deployed solar arrays surface and points along the HGA pointing direction; - +Y completes the right hand frame; - the origin of this frame is at the center of the launch vehicle interface ring attached to the shield side of the spacecraft bus. This diagram illustrates the spacecraft reference frame and DFMI mounting with respect to it: Solar Array Whipple Shield +Z .-. Shield .-. ^| | | |==========|====o===============o=============== `-' || |-------------------. Solar ------> ------> || |<--DFMI sensors are| Array Nominal || | .-----. on the | Incoming <-------o| | | ' Whipple | Particle +X +Y .CIDA_/ Shield | direction | | `. `. | during | |--- `. `.---- -----' Encounter | | `. ` `-' `.'`. .' As seen on the diagram DFMI is located on the +X side of the spacecraft bus. The DFMI target plane is parallel to the spacecraft YZ plane, and the particles are coming in from the +X direction. Software ======== The data in this data set are in standard PDS format -- ASCII text files with comma-delimited columns -- and, therefore, can be viewed by PDS-provided programs or loaded into commercial programs that support comma-delimited formats. For this reason no special processing software is included in this data set. Contact Information =================== For any questions regarding the data in this archive, contact: Dr. Thanasis Economou, DU, PVDF sensors Dr. Simon Green, Stardust DASS, acoustic sensors.

These data are available on-line from the Planetary Data System (PDS) at:

http://pdssbn.astro.umd.edu/holdings/sdu-c_d-dfmi-2_3-next-tempel1-v1.0/

Alternate Names

  • SDU-C/D-DFMI-2/3-NEXT-TEMPEL1-V1.0

Discipline

  • Planetary Science: Small Bodies

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Mr. Anthony J. TuzzolinoData ProviderUniversity of Chicago
Dr. Thanasis E. EconomouGeneral ContactUniversity of Chicagotecon@tecon.uchicago.edu
[USA.gov] NASA Logo - nasa.gov