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Last modified: Fri Feb 2 17:45:03 2001.
Project : SOHO - CDS
Name : ARCMIN2HEL()
Purpose : Convert arcmin from sun centre to heliographic coords.
Explanation : Converts an (x,y) position given in arcmins relative to the
solar disk centre to heliographic coordinates for the date
supplied ( default date = today).
Use : IDL> helio = arcmin2hel(xx,yy,date=date)
Inputs : xx - E/W coordinate in arc minutes relative to sun center
(West is positive)
yy - S/N coordinate in arc minutes relative to sun center
(North is positive)
Opt. Inputs : None
Outputs : Function returns 2 element vector: [lat, long] in degrees.
Opt. Outputs: None
Keywords : date - date/time in any CDS format
off_limb - flag which is true if the coordinates are beyond
the solar limb.
Calls : PB0R
ANYTIM2UTC
Restrictions: If the supplied coordinates are outside the solar disk, the
region is projected onto the limb.
Side effects: None
Category : Util, coord
Prev. Hist. : Original by J P Wuelser.
Written : CDS version by C D Pike, RAL, 6 Sept 93
Modified : Converted to use CDS time and pb0r routines, CDP, 17-May-94
Version 3, William Thompson, GSFC, 14 November 1994
Modified .DAY to .MJD
Version : Version 3, 14 November 1994
Project : SOHO - CDS
Name : HEL2ARCMIN()
Purpose : Compute position relative to sun centre from heliographic.
Explanation : Using the input heliographic coordinates of a feature,
calculate the position in arcmin relative to the sun centre
taking account of the sun's orientation (B0). The current
date is assumed unless specified. West and North are
considered positive.
Use : IDL> print, hel2armin(ns, ew, date = dat)
eg print,hel2arcmin('S34','E23')
or print,hel2arcmin(-34,-23)
Inputs : ns - the Heliographic latitude in degrees (can be a
string with N/S first character instead of sign).
ew - the Heliographic longitude in degrees (can be a
string with E/W first character instead of sign).
Opt. Inputs : None
Outputs : Function returns the (x,y) location in arcmins relative to
sun disk centre.
Opt. Outputs: None
Keywords : date - the date to use in the calculation of B0.
Calls : PB0R
ANYTIM2UTC
Restrictions: None
Side effects: None
Category : Utilities, coordinates.
Prev. Hist. : Yohkoh routine by Hudson/Wuelser.
Written : CDS version, C D Pike, RAL, 6 Sept 93
Modified : To use CDS time and pb0r routines, CDP, 17-May-94
Version 2, William Thompson, GSFC, 14 November 1994
Modified .DAY to .MJD
Version : Version 3, 14 November 1994
Project : SOHO - CDS
Name : PB0R()
Purpose : To calculate the solar P, B0 angles and the semi-diameter.
Explanation : Uses semi-rigorous formulae to calculate the solar P (position
angle of pole) and B0 (latitude of point at disk centre) angles
and also the semi-diameter of the solar disk at the date/time
requested.
Use : IDL> ang = pb0r(date_time)
Inputs : date_time - the date/time specified in any CDS format
Opt. Inputs : None
Outputs : Function returns a 3-element array with
ang(0) = P (degrees)
ang(1) = B0 (degrees)
ang(2) = R semi-diameter (arcmin)
Opt. Outputs: None
Keywords : None
Calls : ANYTIM2UTC
SUN_POS
Common : None
Restrictions: None
Side effects: None
Category : Util, coords
Prev. Hist. : Based on Fortran programs by Hohenkerk and Emerson (RGO)
Written : CDS/IDL version, C D Pike, RAL, 16-May-94
Modified : Update semi-diameter calculation, CDP, 20-May-94
Version 3, William Thompson, GSFC, 14 November 1994
Modified .DAY to .MJD
Version : Version 3, 14 November 1994
PROJECT:
SOHO - CDS
NAME:
ROTATION()
PURPOSE:
Make a 3x3 matrix for a rotation transformation conversion.
EXPLANATION:
CALLING SEQUENCE:
Result = ROTATION(axis_id, angle)
INPUTS:
axis_id -- An integer that indicates the axis about which the system
is rotated. For x, y, and z axes, the value is 1, 2, and 3
respectively.
angle -- Angle of rotation in radians. Positive value indicates a
rotation that follows the right-hand rule.
OPTIONAL INPUTS:
None.
OUTPUTS:
Result -- A 3x3 two-dimensional array, the transformation matrix
OPTIONAL OUTPUTS:
None.
KEYWORD PARAMETERS:
None.
CALLS:
None.
COMMON BLOCKS:
None.
RESTRICTIONS:
None.
SIDE EFFECTS:
None.
CATEGORY:
Utilities, coordinates
PREVIOUS HISTORY:
Written in Fortran by Liyun Wang, UF, January 17, 1988
MODIFICATION HISTORY:
Written September 8, 1994, by Liyun Wang, GSFC/ARC
VERSION:
Project : SOHO - CDS
Name : SUN_POS
Purpose : Calculate solar ephemeris parameters.
Explanation : Allows for planetary and lunar perturbations in the calculation
of solar longitude at date and various other solar positional
parameters.
Use : IDL> sun_pos, date, longitude, ra, dec, app_long, obliq
Inputs : date - fractional number of days since JD 2415020.0
Opt. Inputs : None
Outputs : longitude - Longitude of sun for mean equinox of date (degs)
ra - Apparent RA for true equinox of date (degs)
dec - Apparent declination for true equinox of date (degs)
app_long - Apparent longitude (degs)
obliq - True obliquity (degs)
Opt. Outputs: All above
Keywords : None
Calls : None
Common : None
Restrictions: None
Side effects: None
Category : Util, coords
Prev. Hist. : From Fortran routine by B Emerson (RGO).
Written : CDS/IDL version by C D Pike, RAL, 17-May-94
Modified :
Version : Version 1, 17-May-94