ACKNOWLEDGMENT::

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Before July 2017:

The general aspect of the filename is:

xxyymmdd.hhnnss.fits where

yy are the last two digits of the year, mm is the month, dd is the day, hh the hour, nn the minutes and ss the seconds.

Data are in FITS format.

xx value is:	mh for H alpha images (chromosphere)
	mk for Ca II K1 images (wing of the line, photosphere)
	mK for Ca II K3 images (center of line, chromosphere)
	mp for Ca II K3 prominences

Two time periods must be considered for spectroheliograms:

• Before the 13th of Mai, 2002: Observations are made with photographic plates, then scanned to be digitalized (hereafter period 1)
• Beginning from the 13th of Mai, 2002: Observations are obtained from a CCD camera (hereafter period 2)

For a scientific purpose, use the FITS files (14 bits) instead of th GIF Files (8 bits).
Flat field will be available later to improve the images.

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H alpha spectroheliograms

Wavelength of observation: 6562.8 Angstroems.

Example of filename: mh020530.071524.fits (FITS format)

	Period 1	Period 2
Header	5760 bytes	2880 bytes
Image size	928x942	1500x1340
Number of images per file	1	5
Encoding	16 bits, 12 bits used	16 bits, 14 bits used

These data are also available with a coordinate grid surimposed.

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Ca II K1 spectroheliograms

Wavelength of observation: 3933.2 Angstroems.

Example of filename: mk020530.071524.fits (FITS format)

	Period 1	Period 2
Header	5760 bytes	2880 bytes
Image size	906x917	1500x1340
Number of images per file	1	1
Encoding	16 bits, 12 bits used	16 bits, 14 bits used

These data are also available with a coordinate grid surimposed.

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Ca II K3v spectroheliograms

Wavelength of observation: 3933.7 Angstroems.

Example of filename: mK020530.071524.fits (FITS format)

	Period 1	Period 2
Header	5760 bytes	2880 bytes
Image size	928x942	1500x1340
Number of images per file	1	5
Encoding	16 bits, 12 bits used	16 bits, 14 bits used

These data are also available with a coordinate grid surimposed.

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Ca II K3p prominences spectroheliograms

Wavelength of observation: 3933.7 Angstroems.

Example of filename: mp020530.071524.fits (FITS format)

	Period 1	Period 2
Header	5760 bytes	2880 bytes
Image size	976x1002	1500x1340
Number of images per file	1	1
Encoding	16 bits, 12 bits used	16 bits, 14 bits used

- More infos

Movies and curves (until october 2004)

The Meudon heliograph allows the observation of the full sun at different wavelengths in the H alpha line. The Lyot filter has a passband of 0.5 A. Currently, we make 3 images every minute: H alpha centre, H alpha + 0.5 A and H alpha -0.5 A. It is also possible to have H alpha + 1.0 A and H alpha - 1.0 A under request. The detector is a 1536 x 1024 CCD array and data are registered in FITS format (12 bits, values in the range 0 to 4095). The pixel size is 1.95 arc sec. FITS data are written on CD ROM and are not available in the data base. We just offer in BASS2000 quick look MPEG and QuickTime movies in a reduced format (4 arc sec/pixel), in H alpha centre and wings, and with a time resolution of 2 mn. We provide also light curves in POSTSCRIPT and GIF format to identify flare times.

Requests for FITS original data must be sent to this address.

The filenames are in the form:

haYYMMDD.mpg, h+YYMMDD.mpg for MPEG files and haYYMMDD.mov for QuickTime files (MOVIES), haYYMMDD.ps for POSTSCRIPT files and haYYMMDD.gif for GIF files (LIGHT CURVES in units of CCD counts, maximum 4095).

The field YYMMDD is the date of observation, where YY is the year, MM is the month and DD is the number of the day.

G Band at 430.6 nm

Filter bandwidth

Frequencies of observations: 164 MHz and 327 MHz

Example of filename at 164 MHz: na020530.071524.fits (FITS format)

Example of filename at 327 MHz: nb020530.071524.fits (FITS format)

File format is the same for both frequencies:

Header	5760 bytes
Image size	256x256
Number of images per file	1
Encoding	32 bits (floating point numbers)

Nançay radioheliograph data are also available in the following formats:

• movies (MPEG format)
• radio global flux
• radio N/S-E/W plots
• integrated data: Time resolution of integrated files is 32 seconds before 19 april 1999 and 10 seconds after.
• quicklook data: Time resolution of quicklook files is 128 seconds before 19 april 1999 and 120 seconds after.

    The standard name for NRH files is
        nrh2_FFFF_XNI_YYYYMMDD_HHMMSS.CC_T.fts
                        FFFF    frequency , unit 100kHz
                        X            File type:   h     image file
                                                    s    source tracking result
                                                    p    pixel coordonates
                                                    f    flux result
                        N        Number of pixels = 2^N
                        I        free for user purpose
                        YYYYMMDD    Date
                        HHMMSS.CC    Time
                        T        Type        q    time resolution 128s
                                                   i    time resolution 10s or 32s
                                                   c    compressed file, full resolution (available on request to the NRH team)

    Image files
        Image file format uses binary table extension
        EXTENSION 0
            HEADER0:    General information
            No data

        EXTENSION 1
            HEADER1:    Observation and binary table description
            DATA            in binary table
                    1st column    time in milliseconds (TIME)
                    2nd                image number
                    3th                 image for Stokes parameter I (STOKESI)
                    4th                 optionally image for STOKES parameter V (STOKESV)

    Source tracking files
      EXTENSION 0
            HEADER 0:    General information
            No data

        Same number of extension than sources found by 'Source Tracking'
        EXTENSION N
                    1st column      time in ms (TIME)
                    2nd                Intensity of the maximum of the centroid (INTENSITY)
                    3th                 East-West position in pixels (EWPOS)
                    4th                 North-South position in pixels (NSPOS)
                    5th                 Size of the major axis of the ellipse resulting from the fit to the image (MAJAXIS)
                    6th                 Size of the minor axis of the ellipse (MINAXIS)
                    7th                 Angle of the ellipse with respect to the east-west direction (ANGLE)
                    8th                  Flux (FLUX)

        The dimension for MAJAXIS or MINAXIS is 1/Npixels^2. The dimension in solar radius is
                Dim = IND_RS( 1/SQRT(majaxis value), 0, value of SOLAR_R keyword)

    Pixel coordonate files
        These files are ASCII files

    Flux files
        EXTENSION 0
            HEADER 0:    General information
            No data

        Same number of extension than flux computation made on the same images file
        EXTENSION N
                    1st column    time (TIME)
                    2nd                Flux (FLUX)

NRH Whole Sun Flux
    The NRH Group provides daily observation of whole Sun flux intensity at10 frequencies from150MHz to 450 MHz, during 10 hours of each day (from 8 UT TO 16 UT). The data can be loaded from the search form.
    Filename
        nrot_YYYYMMDD_HHMMSS.fts
                YYYYMMDD and HHMMSS date and time of observation

    NRH global flux data are stored in FITS files using binary EXTENSION.

    HEADER 0
        General information about the observation

    EXTENSION 1
        HEADER 1
            format description
        DATA
            Column 1    Time    in milliseconds of the day
            Column 2    flux        2 dimensions array with 10 frequencies (1st dimension frequency, 2nd time)
                                            the frequency range in the array is given by the keyword FREQn in Header 0

            The time resolution is given in the Header by the keyword TIMESTEP (usually 10 ms)

        Software to read and plot flux is available in the NRH tree of Solar Soft
        This software is run by the NRHR command in the SSWIDL environnement
 

Frequencies of observations: from 20 to 75 MHz

Kind of data: Dynamic spectra (frequency as a function of time)

Full data (available with authorization)

• Filename: syymmdd.RT1 where yy, mm and dd are respectively the year, month and day
• Data format:

A 405 bytes header followed by n blocks of 405 bytes in the following order: header, left polarization, right polarization, left polarization, ...

Header format for data beginning the 24th of February, 1994:

byte 1	Nothing
bytes 2-3	Minimum frequency, in MHz (2 bytes)
bytes 4-5	Maximum frequency, in MHz (2 bytes)
bytes 6-8	Spectral resolution, in kHz (3 bytes)
bytes 9-11	Reference intensity, in dBm (3 bytes)
bytes 12-16	Spectral scanning velocity, in ms (5 bytes)
bytes 17-18	Dynamic scale of analyzer, in dB/division (2 bytes)
bytes 19-22	Hour, minutes of the passage of the Sun at the meridian (4 bytes: hhmm)
bytes 23-405	Nothing (383 bytes)

Header format for data before the 24th of February, 1994:

byte 1	Nothing
bytes 2-3	Minimum frequency, in MHz (2 bytes)
bytes 4-5	Maximum frequency, in MHz (2 bytes)
bytes 6-8	Spectral resolution, in kHz (3 bytes)
bytes 9-11	Reference intensity, in dBm (3 bytes)
bytes 12-14	Spectral scanning velocity, in ms (3 bytes)
bytes 15-16	Dynamic scale of analyzer, in dB/division (2 bytes)
bytes 17-20	Hour, minutes of the passage of the Sun at the meridian (4 bytes: hhmm)
bytes 21-405	Nothing (385 bytes)

Format of each data block:

bytes 1-4	Beginning hour of the spectrum (hour, minute, second, hundredth of second: hhmmsscc)
bytes 5-404	Raw intensities with 400 frequencies linearly placed in points between Fmin and F max (log scale, 1 point = 0.3125 dB)
byte 405	Pointing state

Caution: Scanning velocities indicate 350 ms, but control delays effect is that a spectrum is recorded every 494 ms.

Preview data

These data are integrated over 10 s, summing the two polarizations. They are free of access, in GIF format.

Observing wavelength: 6562.7 Angstroems

Example of filename: pr020530.071524.fits (FITS format)

Header	2880 bytes
Image size	1024x1024
Number of images per file	1
Encoding	16 bits, all used

- More infos

The synoptic maps of the solar activity are in Postscript format. These maps indicate when solar structures appear and disappear during a solar rotation. Absciss is time and ordinate is solar latitude. Solar structures are shown on these maps at their actual latitude during all their lifetime.

Two kinds of synoptic maps are proposed:

• One for prominences
• One for filaments
• One for active centers

The informations used for creating synoptic maps are available in the database when you look for synoptic data.

- Synoptic maps user guide

FITS:

This file format consists in a header, containing useful informations concerning the observation, and data. This informations appear as keywords associated with values. In some cases, there could be a secondary header. Each information line of a header is 80 characters long. And each header is a multiple of 2880 characters (ie bytes). Following are data (ie image or images), consisting in one or several arrays of NxP elements, in 8, 16 or 32 bits formats, depends on what is indicated in the header.

The following keywords give useful informations in order to be able to read data:

• EXTEND: if it has the value 'T' (for 'True'), it means that a secondary header exists, which contains informations on data
• NAXIS: Gives the number of dimensions of data array. If it's 0, it means that no data follow (so data must be after the secondary header). If its value is 2, on image follows. If its value is 3, it means that several images follow.
• NAXIS1: gives the first dimension of the image
• NAXIS2: gives the second dimension of the image
• NAXIS3: if it exists, gives the number of images that follow
• BITPIX: Gives the number of bits on which data are encoded: 8 means 1 byte per value, 16 means 2 bytes (ie integer value), 32 or -32 means 4 bytes (ie floating point value).

Click here to see an example of a FITS header.

Extension of FITS files is '.fits' or '.fts'.

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GIF:

These files can be read by most graphic softwares. Data are 8 bits encoded without loosing informations (except if original data are encoded with more than 8 bits, of course).

Extension of GIF files is '.gif'.

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PNG:

These files can be read by most graphic softwares. Data are 16 bits encoded, without loosing informations (except if original data are encoded with more than 16 bits, of course).

Extension of PNG files is '.PNG'.

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JPEG:

These files can also be read by most graphic softwares. Data are 8 bits encoded if they are black and white, and 32 bits encoded for color. JPEG images are compressed, with a loose of informations. But the size of the file is much smaller.

Extension of JPEG files is '.jpeg' or '.jpg'.

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PS (postcript):

Postcript is a vectorial image encoding, so the image can be reduced or raised without lack of informations. This format is specifically usefull for printing. Most laser printers can use postcript format, but generally not ink printers. You can preview postcript files on screen using some specific softwares, such as GHOSTVIEW with UNIX, MacGhostView with Macintosh, XXX with LINUX, or XXX with Windows.

Extension of postcript files is '.ps'.

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Compressed files:

Some filenames have a '.z' extension. It means that they are compressed so as to reduce their size. The compression scheme used is "zip" compression (they are "zipped files") . To uncompress these files, you must use gunzip with UNIX, 'UnZip' or 'StuffIt Expander' softwares with Macintosh, XXX with LINUX, or XXX with Windows.