Helios CD-ROM Documentation ---------------------------------------------------------------------------- Credits The principal investigator (PI) of the Helios plasma instruments (E1) is Dr. Helmut Rosenbauer (MPAe); the PI of the Helios magnetometer instrument (E2) is Prof. Fritz M. Neubauer (Universitaet Koeln). The rights for use of the data remain with the PIs. The responsibility for the production of this data set is with Dr. Rainer Schwenn and Kevin Ivory (MPAe). Parts of the data may be different or missing (compared to other data sets), due to various processing routines used over the years. Katlenburg-Lindau, January 22, 1996 Max-Planck-Institut fuer Aeronmomie (MPAe) Postfach 20 D-37189 Katlenburg-Lindau Max-Planck-Strasse 2 D-37191 Katlenburg-Lindau GERMANY Directory Structure The label of the CD-ROM is HELIOSCD. HELIOSCD | +---- BIN -- HELIOS1 contains binary data files | +------ HELIOS2 | +---- DOC contains documentation on directory and | file structures on the CD-ROM | +---- PROG contains Fortran programs (used to generate | the files and usable to read the binary files) | +---- TAB -- HELIOS1 contains table data files (ASCII text) +------ HELIOS2 All files were created on a DEC Alpha system running under DEC Unix. That means that the binary data is stored in little-endian IEEE format and the ASCII data is stored with LF denoting the end-of-line. For systems that denote the end-of-line with CRLF, the GNU free software program 'recode' can be used to transform the notation. The CD-ROM was written in accordance to the ISO 9660 filesystem standard with Rock Ridge extension attributes. We were able to successfully read all files from the CD-ROM with the operating systems DEC Unix, OpenVMS and MS-DOS/Windows. On each of these systems we were also successful in reading the binary files with Fortran programs. Some operating system dependent hints: * DEC Unix The mount command used was the following: $ mount -r -t cdfs -o noversion /dev/.... /cdrom * Open VMS The mount command varies depending on file type o for text files and tables: $ MOUNT/MEDIA=CDROM/UNDEF=(STREAM_LF:159) device [volume] [logical] o for binary files: $ MOUNT/MEDIA=CDROM/UNDEF=(FIXED:NONE:80) device [volume] [logical] (the volume-label is HELIOSCD) * DOS/Windows Text files and tables must be converted from Unix format to DOS format (end-of-line: LF -> CRLF). There are many public domain and free software utilities to do this (e.g. CRLF.COM or RECODE.EXE). Table File Structure For each day and spacecraft a separate table file is supplied in the tab directory of this CD-ROM. If no data is available for a particular day, there is no file for that day. The files are named something like h178_058.tab, where h1 or h2 stands for the spacecraft Helios 1 or Helios 2, 78 stands for the year 1978, followed by a single underline and the day of year written with three digits. Each file has the extension .tab. The files were created on DEC Alpha system running under DEC Unix with the Fortran program cd_tab (cd_tab.f) supplied in prog directory of the CD-ROM. They are in ASCII text format and the end of line is denoted by LF (for DOS/Windows systems convert to CRLF). Each file begins with two comment lines (the first 8 characters of the first line give year and day of year of the following lines). Each data spectrum is stored in a 159 byte (=column) record (plus LF) of the following format: Column Format Type Parameter 1- 2 i2 INTEGER hour (time format: hh:mm:ss) 4- 5 i2 INTEGER minute 7- 8 i2 INTEGER second 9- 13 f5.2 REAL heliocentric distance of s/c [AU] 14- 20 f7.2 REAL earth-sun-s/c angle [deg] 21- 27 f7.2 REAL Carrington longitude of s/c [deg] 28- 33 f6.2 REAL Carrington latitude of s/c [deg] 34- 38 i5 INTEGER Carrington rotation # 39- 45 f7.2 REAL I1A proton density [cm-3] 46- 53 f8.1 REAL I1A proton velocity [km/s] 54- 61 f8.0 REAL I1A proton temperature [K] 62- 67 f6.2 REAL I1A proton azimuthal flow angle [deg] 68- 73 f6.2 REAL I1A proton elevational flow angle [deg] 74- 80 f7.2 REAL E2 magnetic field, Bx [nT] 81- 87 f7.2 REAL E2 magnetic field, By [nT] 88- 94 f7.2 REAL E2 magnetic field, Bz [nT] 95- 99 f5.2 REAL E2 magnetic field, sigma Bx [nT] 100-104 f5.2 REAL E2 magnetic field, sigma Bx [nT] 105-109 f5.2 REAL E2 magnetic field, sigma Bx [nT] 110-115 f6.2 REAL I1A alpha density [cm-3] 116-121 f6.1 REAL I1A alpha velocity [km/s] 122-129 f8.0 REAL I1A alpha temperature [K] 130-135 f6.2 REAL I1B proton density [cm-3] 136-141 f6.1 REAL I1B proton velocity [km/s] 142-149 f8.0 REAL I1B proton temperature [K] Missing plasma parameters have the value -1, missing magnetic data have the value 0. With VMS, the CD-ROM will have to be mounted with an option specifying stream records with a maximum of 159 bytes to successfully read/copy the *.tab files: $ MOUNT/MEDIA=CDROM/UNDEF=(STREAM_LF:159) device [volume] [logical] (the volume-label is HELIOSCD) Binary File Structure For each day and spacecraft a separate binary file is supplied in the bin directory of this CD-ROM. If no data is available for a particular day, there is no file for that day. The files are named something like h178_058.cd, where h1 or h2 stands for the spacecraft Helios 1 or Helios 2, 78 stands for the year 1978, followed by a single underline and the day of year written with three digits. Each file has the extension .cd. The files were created on DEC Alpha system running under DEC Unix, which means that the binary data is stored in little-endian IEEE format. This is the same format used on systems based on the Intel x86-series and on Digital DECstations. On HP, Sun, IBM and other similar workstations, big-endian IEEE format is common, so byteswapping may be necessary with such systems. Each data spectrum is stored in a 80 byte record of the following format (byte count starts with 1, bit counts start with 0): Bytes (1-80) Type Parameter 1 - 4 INTEGER*4 datetime Bits 0-30 datetime, seconds since Jan 1, 1964 time = MOD(datetime,86400) sec of day date = datetime/86400 days since 010164 31 spacecraft (0: Helios 1, 1: Helios 2) 5 - 8 INTEGER*4 imode Bits 0 I1A protons (0: available, 1: not) 1 I1A alphas (0: available, 1: not) 2 I1B protons (0: available, 1: not) 3 E2 magnetic field (0: available, 1: not) 4 I1B electrons (0: available, 1: not) 5 alternating shift (0: no, 1: yes) 6 perihel shift (0: no, 1: yes) 7 data mode (0: normal, 1: high) 8- 9 format (0: 5, 1: 1, 2: 2, 3: 3) 10-13 log2(bitrate) (3: 8, ... , 12: 4096) 14-15 unused 16 distribution mode 7 (0: no, 1: yes) 17-23 unused 24-31 Carrington rotation # - 1600 9 - 24 REAL*4 orbit(4) orbital parameters of the Helios s/c array element 1 heliocentric distance of s/c [AU] 2 earth-sun-s/c angle [deg] 3 Carrington longitude of s/c [deg] 4 Carrington latitude of s/c [deg] 25 - 44 REAL*4 p_i1a(5) I1A proton parameters array element 1 density [cm-3] 2 velocity [km/s] 3 temperature [K] 4 azimuthal flow angle [deg] 5 elevational flow angle [deg] 45 - 56 REAL*4 a_i1a(3) I1A alpha parameters array element 1 density [cm-3] 2 velocity [km/s] 3 temperature [K] 57 - 68 REAL*4 p_i1b(3) I1B proton parameters array element 1 density [cm-3] 2 velocity [km/s] 3 temperature [K] 69 - 80 INTEGER*2 m_e2(6) E2 magnetic field array element 1 Bx [100 nT] 2 By [100 nT] 3 Bz [100 nT] 4 sigma Bx [100 nT] 5 sigma By [100 nT] 6 sigma Bz [100 nT] Missing plasma parameters have the value -1, missing magnetic data have the value 0. The Fortran open statement may differ depending on the compiler and system used. If the record length has to be given in bytes, the open statement will be OPEN (15, FILE='h178_058.cd', ACCESS='DIRECT', RECL=80, & STATUS='OLD') If the record length has to be given in words, the open statement will be OPEN (15, FILE='h178_058.cd', ACCESS='DIRECT', RECL=20, & STATUS='OLD') With DEC Fortran for OpenVMS you may also have to use the option CONVERT='LITTLE_ENDIAN'. With VMS, the CD-ROM may either have to be mounted with an option specifying the fixed record length of 80 bytes: $ MOUNT/MEDIA=CDROM/UNDEF=(FIXED:NONE:80) device [volume] [logical] (the volume-label is HELIOSCD) or with OpenVMS 6.0 or higher, the file attributes may be changed later with the following command: $ SET FILE/ATTRIBUTE=LRL:80 *.CD Appendix: ISO 9660 Filesystem History In the past years compact discs originally developed by the Philips and Sony companies for recording music have also been used for recording data as they allow recording of large amounts of information in a reliable and economic manner. As a read-only medium they are particularly suitable for use in applications such as auditing and legal documents. It appeared very quickly that there is an urgent need for public standards for this medium. In October 1985, a number of industrial and software companies in the USA invited experts to participate in the elaboration of a working paper describing a proposal for the volume and file structure for such disks. The result of this work, in which also expert members of ECMA/TC15 as well as from Japan participated, was a report dated May 1986 and known as the "High Sierra Group" proposal. This proposal was submitted to ECMA for their consideration. ECMA TC15, in collaboration with experts from user organizations, invested a considerable amount of work into this proposual in order to clarify and complete its technical contents and to re-edit it in a form suitable for an international standard. This led to the issue in December 1986 of Standard ECMA-119 which has been adopted by ISO as International Standard ISO 9660. ISO 9660 Image An ISO 9660 image can be divided into five parts: System Area The first 16 blocks of an ISO 9660 image are in most cases unused. Volume Descriptor Block 16 of an ISO 9660 image contains all image information. Path Tables The path tables contain information on all CD-ROM directories and are intended to speed up directory access. Directories The directories of an ISO 9660 image contain pointers to the subdirectories and files located in that directory. Files The files of an ISO 9660 image contain the user data. Restrictions ISO 9660 is a filesystem for nearly all computer platforms; filenames and directories are restricted to the set available on all machines: * Filenames must contain only the characters from 'A' to 'Z', numbers from '0' to '9' or the character '_'. * A valid ISO 9660 filename must contain a '.' character. * Before the '.' there are up to 8 characters allowed, after the point up to three. * Directory names must not contain a '.' character and their length is restricted to 8 characters. * The directory depth must not exceed 8 levels.