Document title: Format and data set description for the NDADS DE datatype WATS_2S_ASCII. Project: DE NDADS Datatype: WATS_2S_ASCII EID: DOCUMENT Super-EID: DOCUMENTS There may be other documents also identified by this super-EID. NDADS filename: wats_readme_de.doc TRF entry: b47611.txt in NSSDC's controlled digital document library, Dec. 1998. Document text follows: ---------------------- DE-2 Wind and Temperature Spectrometer (WATS) data on NDADS ___________________________________________________________ This data set consists of the high-resolution data of the Dynamics Explorer 2 Wind and Temperature Spectrometer (WATS) experiment. The files contain the neutral density, temperature and horizontal (zonal) wind velocity, and orbital parameters in ASCII format. The time resolution is typically 2 seconds. Data are given as daily files (typically a few 100 Kbytes each). PI-provided software (WATSCOR) was used to correct the binary data set. NSSDC-developed software was used to add the orbit parameters, to convert the binary into ASCII format and to combine the (PI-provided) orbital files into daily files. For more on DE-2, WATS, and the binary data, see the WATS_VOLDESC_SFDU_DE.DOC and WATS_FORMAT_SFDU_DE.DOC files. More information about the processing done at NSSDC is given in WATS_NSSDC_PRO_DE.DOC. The WATS files can be accessed on NDADS/Spycat at http://nssdc.gsfc.nasa.gov/space/ndads/spycat.html They can be also obtained through automated mail request from archives@ndads. gsfc.nasa.gov (use subject:request de wats_ascii and your dates of interest yyddd in the body of the message. The data files are then staged as yyddd_WATS_DE_2S_V01.ASC; yy is the year, ddd is the day of the year. The date range for the WATS files is 81220-83049 with most days represented. ------------------------------------------------------------------------------ Format of yyddd_WATS_DE_2S_V01.ASC Files ------------------------------------------------------------------------------ Each data record contains the following data (if there is no data for a given parameter, or if the parameter is clearly outside the valid range, a fill value of -9.0 is given (9999 for velocity-words 10, 15 and 16; 9 for baffle direction and slot position, word 3 and 4): 1 - date (I5) [yyddd] 2 - UT (I9) [ms] 3 - Mode (I2) =3,4 measuring the horizontal velocity =5,6 measuring the vertical velocity 4 - Slot (I1) =1,2,3,4; steps from 1 to 4 during each 8-sec measurement sequence, mode may change at each step. 5 - Outin (I1) =1 baffle going out, =0 going in 6 - Mass (I3) [AMU] Usually 28 or 32 (32 is assume to be mostly atomic oxygen which is recombined in the instrument). 7 - Density (E12.5) [cm-3] Density of neutrals with mass given in Word 6 (negative values should be ignored). 8 - Tn (F7.1) [K] Neutral temperature of neutral with mass given in word 6. 9 - Tn_corr* (F7.1) [K] Neutral temperature after WATSCOR correction. 10 - V_s/c (F8.1) [m/s] Horizontal (zonal) velocity (of neutrals with mass given in word 5) if Mode=3,4. Velocity is given in spacecraft spacecraft coordinates (positiv in the Z-axis direction). Vertical velocity in s/c coordinates (positive in the Y axis direction) if Mode=5,6. 11 - C1** (1X,I5) (Instrument counts)/8 12 - C2 (I5) (Counts + background)/8 13 - T1*** (1X,I3) [2s/255] Time when the baffle crosses the first optical position sensor. 14 - T2*** (I3) [2s/255] Time when the baffle crosses the second optical position sensor. 15 - V_geo (/F8.1) [m/s] Horizontal/vertical (zonal) velocity in corotating Earth frame (positive in the eastward/upward direction) if mode=3,4/5,6. 16 - V_geo_cor* (F8.1) [m/s] Velocity (word 15) after WATSCOR correction* 17 - Orbit (I6) orbit number 18 - Altitude (F7.1) [km] 19 - Latitude (F6.1) [degree] geographic latitude 20 - Longitude (F7.1) [degree] geographic latitude 21 - LST (F6.2) [hours] Local Solar Time 22 - LMT (F6.2) [hours] Local Magnetic Time 23 - L (F5.2) McIllwain L value 24 - Inv. Lat. (F6.1) [degree] Invariant latitude 25 - SZA (F7.1) [degree] Solar Zenith Angle * Temperatures and velocities for atomic oxygen are corrected for errors due to absorption of atomic oyxygen in the metallic surfaces. The temperature and velocity measurements for nitrogen are taken as reference in obtaining the calibration factors. For studies only requiring the AC variation (e.g., gravity wave analysis) it is recommended to use the uncorrected data since the correction will distort the spectrum. If a correct DC level is required (e.g., ion-neutral momentum and energy transfer) the corrected values should be used. ** The instrument counts can be used to calculate the statistical error as explained in the WATS_.._SFDU_DE.DOC files: STn/Tn = 1.3 / SQRT(C1) SV = 260 / SQRT(C1) ST and SV are the standard deviation of the temperature and velocity measurement, respectively. Tn is the temperature measurement (Word 7 or 8), and C1 is Word 11. *** A full baffle swoop corresponds to 2 s. The time resolution is limited to 2s/255, because the orignal parameter value is encode in a 2-bit word. ------------------------------------------------------------------------------ README files and Software for this data set ------------------------------------------------------------------------------ The text files describing this data set in more detail can be accessed through URL links from the holdings file. The following text files are provided: format.sfd Description of the format of the original data provided by the PI team. voldesc.sfd Brief description of the experiment and the original PI-provided data set. readme.doc Description of this data set nssdc_pro.doc Description of processing done at NSSDC The following FORTRAN software was used to generate this data set from the original data set. The software files are accessible through the holdings file: watscor.for PI-provided software for data correction. oawatsread.for This NSSDC-developed program was used to add the orbit parameters and to split the orbit files into daily files. Output data are in ASCII format. This program requires the subroutine file OAREAD.FOR and the orbit database OABASE.DAT. The OABASE.DAT file is available on NDADS/Spycat under project=DE, data_type=orbit, entry_ID=orbit_oa_de.bin. oaread.for subroutine for reading the orbit/attitude database oabase.dat. ------------------------------------------------------------------------------