;+
;       NAME:
;               nh_alt.Pro
;
;       PURPOSE:
;		Returns the altiude and azimuth of the New Horizons spacecraft as seen from a given location.
;      
;
;	DESCRIPTION:
;		Load the meta kernel file into naif.  Get the RA and Dec of New Horizons, the latitude and longitude of
;		the specified station (currently the 70-m antennas at Goldstone and Canberra are supported), then 
;		calculate the altitude and azimuth of the spacecraft at the specified JD.
;
;       CALLING SEQUENCE:
;               nh_alt, dsnName, jd, alt, az
;
;       INPUTS:
;       dsnName    - a string for the DSN station: either "Goldstone" or "Canberra"
;		jd	 - the JD at which you want to know the altitude.
;
;       OUTPUTS:
;       alt   - the altitude of the New Horizons spacecraft over the dsn station in dsnName
;		az  - the azimuth of the New Horizons spacecraft over the dsn station in dsnName
;
;       REVISON HISTORY:
;       09-December-2004 CBO SwRI
;-

pro	nh_alt, dsnName, jd, alt, az, load_kernels=lk


	;check to see if optional arguments are set by the user.  If not assign values.
    IF not keyword_set(load_kernels) THEN load_kernels = "FALSE"

;	Load kernels if requested
	if load_kernels EQ "TRUE" THEN naif
	
; Convert time from JD to et
	jdstring = "JD " + string(jd)
	cspice_str2et, jdstring, et

; Get DSN station information
	IF (dsnName EQ "Goldstone") OR (dsnName EQ "goldstone") THEN dsn = "DSS-14" $
	ELSE  IF (dsnName EQ "Canberra") OR (dsnName EQ "canberra") THEN dsn = "DSS-43" $
	ELSE  PRINT, "Station: ", dsnName, "not supported at this time." 
	
;	PRINT, "DSN Station ", dsn
	
; DSS-14 is the 70-m antenna at Goldstone http://www331.jpl.nasa.gov/group8/index.html
; DSS-43 is the 70-meter at Canberra  http://www.cdscc.nasa.gov/Pages/pg02_antennas.html


	CSPICE_BODN2C, dsn, dsncode, found

;	PRINT, "DSN Station Code ", dsncode

	IF found ne 1.0 THEN PRINT, "Error finding code for dsn station: ", dsn
	
	frame='J2000'
	CSPICE_BODN2C, "Earth", earth, found

	CSPICE_SPKEZ, dsncode, et, frame, 'LT', earth, stateDSN, ltime
	
	print, earth
	
	CSPICE_BODVAR, earth, 'RADII', radii_vec
	
	; calculate the flatness coef
	flat = (radii_vec[0] - radii_vec[2])/radii_vec[0]
	
	CSPICE_RECGEO, stateDSN[0:2], radii_vec[0], flat, longitudeDSN, latitudeDSN, altitudeDSN
	print, longitudeDSN*180./!pi
	print, latitudeDSN*180./!pi

; Get the RA and Dec of New Horizons
;	abcorr = 'LT+S' ;aberration correction for light time plus stellar ab
	abcorr = 'LT' ;only correcting for light time, the eq2hor function performs aberration correction

	nhsc = -98

	CSPICE_SPKEZ, nhsc, et, frame, abcorr, earth, stateNH, ltime
	CSPICE_RECRAD, stateNH[0:2], distNH, raNH, decNH
;	print, decNH*180./!pi
;	print, raNH*180./!pi

; Calculate the altitude and azimuth using an astron function.  I haven't found
;	a cspice function yet.  This function expects RA, DEC, lat and longitude in degrees.
	
	factor = 180./!pi
	
	EQ2HOR, raNH*factor, decNH*factor, jd, alt, az, lat = latitudeDSN*factor, longitude=longitudeDSN*factor, $
altitude = altitudeDSN

; ON Friday, left it that there is a problem with getting cspice_recgeo to work.  Need radii and flatness from a 
; kernel file.
	
end

;+


;+
;       NAME:
;               nh_alt1d.Pro
;
;       PURPOSE:
;		Returns the altiude and azimuth of the New Horizons spacecraft as seen from a given location
;		for a day beginning at jd.
;      
;
;	DESCRIPTION:
;		Load the meta kernel file into naif.  Get the RA and Dec of New Horizons, the latitude and longitude of
;		the specified station (currently the 70-m antennas at Goldstone and Canberra are supported), then 
;		calculate the altitude and azimuth of the spacecraft at the specified JD.
;
;       CALLING SEQUENCE:
;               alt = nh_alt1d(dsnName, jd)
;
;       INPUTS:
;       dsnName    - a string for the DSN station: either "Goldstone" or "Canberra"
;		jd	 - the JD at which you want to know the altitude.
;
;       OUTPUTS:
;       alt   - the altitude of the New Horizons spacecraft over the dsn station in dsnName
;
;       REVISON HISTORY:
;       09-December-2004 CBO SwRI
;-

function	nh_alt1d, dsnName, jd


; a ten minute increment:

	jdfrac = 10./(24.*60.)
	n = 6.*24.
	
	altarr = fltarr(n)
	
	FOR i=0, n-1 DO BEGIN
		nh_alt, dsnName, jd + i*jdfrac, alt, az
		altarr[i] = alt
	ENDFOR
	
	return, altarr
	
	END