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Earthshine blog

"Earthshine blog"

A blog about a telescopic system at the Mauna Loa Observatory on Hawaii to determine terrestrial albedo by earthshine observations. Feasible thanks to sheer determination.

What next, for Earthshine observations?

Links to sites and software, Observation Resources, Optical design, Post-Obs scattered-light rem. Posted by peter.thejllPosted on Jul 21, 2021 10:53

We now take the next steps, after building the Mauna Loa system and operating it: into Space with NASA!

The reason is simply that, from space we can avoid the variability due to observing through an atmosphere and do not need a global network of earth-bound telescopes – one suitable instrument will do it all from orbit.

Even from NOAA’s Mauna Loa Observatory (MLO) — one of the best observatories anywhere on Earth — we could easily see variability in our results due mainly to very thin high-altitude clouds. Extinction at MLO is low of course, but variable. Sure, the ‘bad seeing nights’ can be eliminated by detecting the variability each night, but then you end up with not very many good data!

When we noticed a small Earth-Observing student satellite ( @flying_laptop on Twitter) from University of Stuttgart — we asked if they would try to catch some images of the Moon for us — and they did! The images were interesting and taught us the importance of optimized optical design — optimization for the sake of driving down ‘scattered light’ (really, a phrase covering aperture diffraction as well as various internal scattering processes). We worked with the students and reported on what we found at the 2019 annual European Geophysical Union meeting in Vienna, in the “Earth radiation budget, radiative forcing and climate change” session that Martin Wild, and others, organize each year. See our poster here.

Building on that experience, we are now looking at more ways to go into space, and also to improve on the earthshine instruments we can orbit.

One such effort is with the SAIL (Space and Atmospheric Instrumentation Lab) at Embry-Riddle Aeronautical University in Daytona Beach, Florida. With three friends there we are putting together a NASA Instrument Incubator Proposal (IIP) for development of an optical system optimized for the task at hand: observing high-contrast targets with quite extreme requirements for performance.

In our present ground-based approach we are never really observing the Moon without a contribution from the atmosphere, and must resort to various ‘subtraction schemes’ to get rid of either a ‘halo around the Moon’ (which is light scattered along the path to the image sensor) or a ‘flat sky level’ which can be due to such things as airglow, or the Moon-light scattering up from the ground onto particles in the atmosphere (this is not a ‘halo contribution’). Both kinds of contributions have to be removed before the faint earthshine can be used for terrestrial albedo studies. From space, both of these contributions would be omitted automatically, leaving only a faint contribution due to aperture diffraction — our goal is therefore to study how to build a telescope that has as little diffraction as possible.

With our group of experts in optics and satellite payloads at Embry-Riddle we are considering refractive optics, advanced sensors and ‘baffling’ to minimize unwanted light reaching the image sensor. Our IIP proposal is being submitted this week!

We have tried NASA proposals before, and this is the second try, building on reviews of our first attempt. The opportunities — the proposal call aims — vary, so emphasis is different this time: First time we focused on the sensors, now we are working on the optics.



Hoijemakers

Links to sites and software Posted by peter.thejllPosted on Jan 21, 2014 08:43

Henriette sent us this:

Jens Hoijemakers in Leiden wrote a thesis about a telescope you could put on the Moon and monitor Earth with – an earthlight telescope!

He has a YouTube video: http://www.youtube.com/watch?v=AcofvAjVT7Y

His thesis is here:


pdf

And here is a paper.

Thanks Henriette!



Press mentions

Links to sites and software Posted by peter.thejllPosted on Jan 19, 2014 14:01

Our paper, and the story in The Guardian seems to be generating quite a lot of activity on the net. Here is a collection of what I can find:

Original Arxiv.org paper – Jan 9 2014:
http://arxiv.org/abs/1401.1994

From Jan 10 2014:

The Guardian story:
http://www.theguardian.com/science/2014/jan/10/dark-side-moon-turquoise-astronomers

The Economic Times of India – :
http://articles.economictimes.indiatimes.com/2014-01-13/news/46150068_1_dark-side-moon-earth

The Raw Story:
http://www.rawstory.com/rs/2014/01/10/hawaiian-telescope-discovered-the-dark-side-of-the-moon-is-turquoise/

and so on …

http://www.arihantbooks.com/NewsEvents/487/Science-Buzz/Moon-s-dark-side-is-turquoise-in-colour_-claim-experts

CNET: http://news.cnet.com/8301-17852_3-57617095-71/brain-damage-the-dark-side-of-the-moon-is-turquoise/

Several stories captured by a news ‘bot: http://www.newsfiber.com/p/s/h?v=EBXOI5VPyVXw%3D+aivNYXh2b1I%3D

A search on Google gives a lot:
http://goo.gl/NG7049

This search: http://bit.ly/1f2a3fM gave 746 hits on Jan 21 2014.



In The Guardian online version

Links to sites and software Posted by peter.thejllPosted on Jan 11, 2014 08:20

Only a few hours after posting our A&A accepted manuscript on arxiv.org:
http://arxiv.org/abs/1401.1994
we were called up by Ian Sample, a Journalist from The Guardian newspaper, who had noticed the catchy title of the paper – he interviewed, and then he wrote this:
http://www.theguardian.com/science/2014/jan/10/dark-side-moon-turquoise-astronomers

A&A editors have asked us if we would like to have our Figure 1 on the cover of A&A and I said ‘YES!’. They could not promise they would use it – but let’s see.



Nice list of filter properties

Links to sites and software Posted by peter.thejllPosted on Sep 10, 2013 07:50

Here is a link to a site that lists transmission curves of many color filters – e.g. Wratten filters.

It looks like Schott RG665 is most like VE2, and might be the long-pass filter we need on a modified SIgma SD100 camera. We need it with 58mm thread, though.

Wratten #25A is available from B&H with 58mm thread but has its cutoff at 620 nm.

B&H have a 58mm Polaroid that looks ok. Transmits from 720 nm and up.



Colour of sky at night

Links to sites and software Posted by peter.thejllPosted on Jul 02, 2013 15:18

There is a page that discusses the B-V colour of the sky at night: http://www2b.abc.net.au/science/k2/stn/archives/archive8/newposts/60/topic60381.shtm



How to find a comet

Links to sites and software Posted by peter.thejllPosted on Apr 12, 2012 10:34

Comet ephemerids:

link



Historic material on Earthshine

Links to sites and software Posted by peter.thejllPosted on Nov 15, 2011 17:33

Leonardo da Vinci’s notebooks: http://www.fromoldbooks.org/Richter-NotebooksOfLeonardo/section-14/item-902.html

A reference to Humboldt in 1774: http://www.britastro.org/journal/pdf/120-4forum.pdf also, Kepler and Galileo.



Rainbow Angle

Links to sites and software Posted by peter.thejllPosted on Nov 06, 2011 14:53

Table of “Rainbow angle” as seen from MLO. The angle is SEM. Times are UTC. Sun is down.


pdf


Color separation

Links to sites and software Posted by peter.thejllPosted on Nov 03, 2011 08:43

You can use the convert command from ImageMagick to separate JPG images into the R G and B fields easily:

convert -separate -channel R Im.jpg R.jpg
convert -separate -channel G Im.jpg G.jpg
convert -separate -channel B Im.jpg B.jpg



Sunglint software

Links to sites and software Posted by peter.thejllPosted on Oct 30, 2011 15:59

Here is the FORTRAN code that predicts the position of the Sun glint given the position of the Moon and the time.

PROGRAM SUNGLINT_MOON
c—————————————————————————
c code that calculates longitude and latitude of the sunglint
c as seen from the Moon
c—————————————————————————
c compile with: gfortran -O3 -fbounds-check sunglintFORTRAN_moon.f -o sung.exe
c or like this: f77 sunglintFORTRAN_moon.f -o sung.exe
c—————————————————————————
c IMPLICIT DOUBLE PRECISION (A-H,O-Z)
IMPLICIT logical (A-Z)
DOUBLE PRECISION GMT,SANG,DIFF,GLON,GLAT,GLAT1,AERR,GLON1,SLON1
DOUBLE PRECISION SLAT1,DEC1,DLAT,DLON,OLDGLAT1,DEC,RA,ASAT,ZSAT
DOUBLE PRECISION OLDGLON1,GLON2,U1,U2,U3,U4,V1,V2,V3,HANG1,HANG
DOUBLE PRECISION F0,G0,DUDT1,DUDT2,DUDT3,DUDT4,DUDP1,DUDP2,DUDP3
DOUBLE PRECISION DUDP4,HOURANG,ATND,DVDT1,DVDT2,DVDT3,XX1,XX2
DOUBLE PRECISION DVDP1,DVDP2,DVDP3,T1,T2,T3,T4,TEMP1,TEMP2,TEMP3
DOUBLE PRECISION AK,AH,TEMP4,TEMP5,TEMP6,DFDT,DFDP,DGDT,DGDP,JD
DOUBLE PRECISION ALATD,ALOND,ECLAT,ECLON,PI,SLAT,SLON,ALT,AZI
PARAMETER (PI=.3141592654D1)
CHARACTER DATE*15,TIME*8,INSTR*8
INTEGER HOUR,MIN,SEC
c READ IN DATE,TIME(GMT) AND SUB-LUNAR POINT (SLAT,SLON)
PRINT ‘(/5X,A,$)’,’ENTER DATE (DD-MM-YYYY):’
READ ‘(A)’,DATE
PRINT ‘(/5X,A,$)’,’ENTER TIME(GMT) (HH:MM:SS):’
READ ‘(A)’,TIME
PRINT ‘(/5X,A,$)’,’ENTER SUB-LUNAR POSITION (SLAT,SLON)’
READ *,SLAT,SLON
c CONVERT TIME (HH:MM:SS) TO DECIMAL HOURS
WRITE (INSTR,'(A)’) TIME
READ (INSTR,100) HOUR,MIN,SEC
100 FORMAT (3(I2,1X))
GMT=FLOAT(HOUR)+FLOAT(MIN)/.6D2+FLOAT(SEC)/.36D4
c COMPUTE POSITION OF SPECULAR POINT (GLAT,GLON)
CALL ECCS (DATE,GMT,ECLAT,ECLON,JD)
CALL EQCS (DATE,GMT,ECLAT,ECLON,DEC,RA)
CALL NEWRAPH (DATE,GMT,SLAT,SLON,GLAT,GLON,AERR)
CALL GECS(GLAT,GLON,SLAT,SLON,ASAT,ZSAT)
CALL HOCS(DATE,GMT,GLAT,GLON,DEC,RA,ALT,AZI)
PRINT 200,DATE,TIME
200 FORMAT (//,5X,’DATE: ‘,A12,10X,’TIME:-‘,A10,'(GMT)’/)
PRINT 300
300 FORMAT (5X,’POSITION OF SUN :’/5X,17(‘=’)/)
PRINT 400,ECLON
400 FORMAT (5X,’ECLIPTIC LONGITUDE:’,F7.2)
PRINT 500,DEC,RA
500 FORMAT(5X,’DECLINATION:’F9.2/5X,’RIGHT ASCENTION:’,F9.2)
PRINT 600,ALT,AZI
600 FORMAT(5X,’ELEVATION:’,F9.2/5X,’AZIMUTH:’,F9.2/)
PRINT 700
700 FORMAT(5X,’POSITION OF THE MOON:’/5X,27(‘=’)/)
PRINT 800,SLAT,SLON
800 FORMAT(5X,’SUB-LUNAR POINT:(SLAT=’,F6.2,’,SLON=’,F7.2,’)’/)
PRINT 900, ASAT,ZSAT
900 FORMAT(5X,’ELEVATION:’,F9.2/5X,’AZIMUTH:’,F9.2/)
PRINT 905
905 FORMAT(5X,’POSITION OF THE SPECULAR POINT :’/5X,32(‘=’)/)
IF (AERR .EQ. .0D0) THEN
PRINT 910,GLAT,GLON
910 FORMAT (5X,’LATITUDE:’,F9.2/5X,’LONGITUDE:’,F7.2)
ELSE
PRINT 915
915 FORMAT(5X,’GLINT DOES NOT LIE WITH IN THE VIEW AREA’)
END IF
END

DOUBLE PRECISION FUNCTION HOURANG(DATE,GMT,GLON,RA)
IMPLICIT LOGICAL (A-Z)
c IMPLICIT DOUBLE PRECISION (A-H,O-Z)
CHARACTER*15 DATE
DOUBLE PRECISION GMT,GLON,RA,GLON1,HANG
DOUBLE PRECISION LST,GST
GLON1=GLON
IF (GLON1 .GT. .18d3) GLON1=GLON1-.36D3
lst=glon1/.15d2+gst(date,gmt)
IF (LST .GT. .24D2) LST=LST-.24D2
IF (LST .LT. .0D0) LST=LST+.24D2
HANG=(LST-RA/.15D2)
IF (HANG .LT. .0D0) HANG=HANG+.24D2
HOURANG=HANG
RETURN
END

SUBROUTINE NEWRAPH(DATE,GMT,SLAT,SLON,GLAT,GLON,AERR)
IMPLICIT logical (A-Z)
c IMPLICIT DOUBLE PRECISION (A-H,O-Z)
INTEGER KK
DOUBLE PRECISION HSAT,ERAD,PI,RAD,RADI,CDIFF,DEC,RA,SLAT,GLAT
DOUBLE PRECISION GMT,SANG,DIFF,SLON,GLON,GLAT1,AERR,GLON1,SLON1
DOUBLE PRECISION SLAT1,DEC1,DLAT,DLON,OLDGLAT1,jd
DOUBLE PRECISION OLDGLON1,GLON2,U1,U2,U3,U4,V1,V2,V3,HANG1,HANG
DOUBLE PRECISION F0,G0,DUDT1,DUDT2,DUDT3,DUDT4,DUDP1,DUDP2,DUDP3
DOUBLE PRECISION DUDP4,HOURANG,ATND,DVDT1,DVDT2,DVDT3,XX1,XX2
DOUBLE PRECISION DVDP1,DVDP2,DVDP3,T1,T2,T3,T4,TEMP1,TEMP2,TEMP3
DOUBLE PRECISION AK,AH,TEMP4,TEMP5,TEMP6,DFDT,DFDP,DGDT,DGDP
DOUBLE PRECISION ALATD,ALOND,ECLAT,ECLON
CHARACTER*15 DATE
PARAMETER (HSAT=.384d9,ERAD=.6378D7)
c PARAMETER (HSAT=.35786D8,ERAD=.6378D7)
PARAMETER (PI=.3141592654D1)
RAD=PI/.18D3
RADI=.18D3/PI
CDIFF=.1D1/.36D4*RAD
CALL ECCS(DATE,GMT,ECLAT,ECLON,jd)
CALL EQCS(DATE,GMT,ECLAT,ECLON,DEC,RA)
GLAT=(DEC+SLAT)/.2D1
SANG=(.12D2-GMT)*.15D2
IF (SANG.LT. .0D0) SANG=SANG+.36D3
DIFF=dabs(SANG-SLON)
IF (DIFF .GT. .18D3) THEN
DIFF=.36D3-DIFF
GLON=DMAX1(SANG,SLON)+DIFF/.2D1
ELSE
GLON=DMIN1(SANG,SLON)+DIFF/.2D1
END IF
IF (GLON .GT. .36D3) GLON=GLON-.36D3
IF (DIFF .GT. .12D3) THEN
AERR=-.1D1
RETURN
END IF
GLAT1=GLAT*RAD
GLON1=GLON*RAD
SLAT1=SLAT*RAD
SLON1=SLON*RAD
DEC1=DEC*RAD
KK=0
150 KK=KK+1
DLAT=GLAT1-SLAT1
DLON=GLON1-SLON1
OLDGLAT1=GLAT1
OLDGLON1=GLON1
GLON2=GLON1*RADI
HANG=HOURANG ( DATE , GMT , GLON2 , RA)
HANG1=HANG* .15D2*RAD
U1= ( HSAT+ERAD) *DCOS ( DLAT) *DCOS( DLON) -ERAD
U2=DSIN(GLAT1)*DSIN(DEC1)+DCOS(DEC1)*DCOS(GLAT1)*DCOS(HANG1)
U3=DSIN( DLON)
U4=-DCOS(DEC1)*DCOS(GLAT1)*DSIN(HANG1)
V1=HSAT**.2D1+.2D1*ERAD* (ERAD+HSAT)*(.1D1-DCOS(DLAT)*DCOS(DLON))
V2=DCOS ( DLON ) *DSIN (DLAT)
V3=DSIN(DEC1)-DSIN(GLAT1)*U2
F0=DASIN(U1/SQRT(V1) )-DASIN(U2)
G0=ATND(U3 ,V2 ) -ATND(U4 ,V3)
DUDT1=- ( ERAD+HSAT) *DSIN ( DLAT ) *DCOS( DLON)
DUDT2=DCOS(GLAT1)*DSIN(DEC1)-DSIN(GLAT1)*DCOS(DEC1)*DCOS(HANG1)
DUDT3= .0D0
DUDT4=DCOS ( DEC1 ) *DSIN(GLAT1 ) *DSIN(HANG1)
DUDP1=- ( ERAD+HSAT) *DCOS ( DLAT ) *DSIN ( DLON)
DUDP2= .0D0
DUDP3=DCOS( DLON)
DUDP4= .0d0
DVDT1= .2D1*ERAD* (HSAT+ERAD) *DSIN ( DLAT) *DCOS (DLON)
DVDT2=DCOS( DLAT) *DCOS ( DLON)
XX1=-.2D1*DSIN(GLAT1 )*DCOS(GLAT1)*DSIN(DEC1 )
XX2=DCOS(GLAT1) *DSIn(GLAT1)*DCOS(DEC1)*DCOS(HANG1)
DVDT3=XX1+XX2
DVDP1=.2D1*ERAD* (HSAT+ERAD) *DCOS( DLAT) *DSIN (DLON )
DVDP2=-DSIN( DLAT) *DSIN ( DLON)
DVDP3=.0D0
T1=.1D1/(SQRT(.1D1-(U1/SQRT(V1))**.2D1))
T2=.1D1/(SQRT(.1D1-U2**.2D1))
T3=.1D1/(.1D1+(U3/V2)**.2D1)
T4=.1D1/(.1D1+(U4/V3)**.2D1)
TEMP1=(SQRT(V1)*DUDT1-U1*DVDT1/(SQRT(V1)*.2D1))/V1
TEMP2=(SQRT(V1)*DUDP1-U1*DVDP1/(SQRT(V1)*.2D1))/V1
TEMP3=(V2*DUDT3-U3*DVDT2)/V2**.2D1
TEMP4=(V2*DUDP3-U3*DVDP2)/V2**.2D1
TEMP5=(V3*DUDT4-U4*DVDT3)/V3**.2D1
TEMP6=(V3*DUDP4-U4*DVDP3)/V3**.2D1
DFDT=T1*TEMP1-T2*DUDT2
DFDP=T1*TEMP2-T2*DUDP2
DGDT=T3*TEMP3+T4*TEMP5*DVDT3
DGDP=T3*TEMP4+T4*TEMP6*DVDP3
AK=(F0*DGDT-G0*DFDT)/(DGDP*DFDT-DFDP*DGDT)
AH=-(AK*DFDP+F0)/DFDT
GLAT1=GLAT1+AH
GLON1=GLON1+AK
IF (GLON1.LT. .0D0) GLON1=GLON1+.2D1*PI
IF (GLON1.GT. .2D1*PI) GLON1=GLON1-.2D1*PI
IF (GLAT1.LT. -PI/.2D1) GLAT1=-PI-GLAT1
IF (GLAT1.GT. PI/.2D1) GLAT1=PI-GLAT1
ALATD=dabs(GLAT1-OLDGLAT1)
ALOND=dabs(GLON1-OLDGLON1)
IF (ALOND .GT.PI) ALOND=.2D1*PI-ALOND
IF (KK .GT.150) THEN
AERR=-.2D0
RETURN
END IF
IF (ALOND .GT.CDIFF .AND.ALATD .GT.CDIFF) GOTO 150
GLAT=GLAT1*RADI
GLON=GLON1*RADI
AERR=.0D0
RETURN
END

SUBROUTINE ECCS (DATE , GMT , ECLAT , ECLON, JD)
IMPLICIT LOGICAL (A-Z)
c IMPLICIT DOUBLE PRECISION (A-H,O-Z)
DOUBLE PRECISION GMT , ECLAT , ECLON, JD,ELE,ELP,ECC,PI
DOUBLE PRECISION EC,JDEP,RAD,AJDATE,DAYS,AN,M,AM
CHARACTER*15 DATE
PARAMETER (ELE=.279403303D3 ,ELP=.282768422D3)
PARAMETER (ECC=.167131D-1 ,PI=.3141592654D1)
RAD=PI/.18D3
JDEP=.24478915D7
JD=AJDATE(DATE,GMT)
DAYS=JD-JDEP
AN=(.36D3/.365242191D3)*DAYS
M=DINT(AN/.36D3)
AN=AN-(M*.36D3)
AM=AN+ELE-ELP
IF (AM .LT. .0D0) AM=AM+.36D3
EC=( .36D3 /PI ) *ECC*DSIN(Am*RAD)
ECLON=AN+EC+ELE
IF (ECLON .GT. .36d3) ECLON=ECLON-.36D3
IF (ECLON .LT. .0D0) ECLON=ECLON+.36D3
ECLAT=.0D0
RETURN
END

SUBROUTINE EQCS ( DATE, GMT , ECLAT , ECLON , DEC,RA)
IMPLICIT LOGICAL (A-Z)
c IMPLICIT DOUBLE PRECISION (A-H,O-Z)
CHARACTER*15 DATE
DOUBLE PRECISION JD,JDEP,PI,GMT , ECLAT , ECLON , DEC,RA
DOUBLE PRECISION RAD,RADI,T,EP,ECLON1,ECLAT1,TEMP1,TEMP2
DOUBLE PRECISION AJDATE,DEP,ANR,DNR,ATND
PARAMETER (PI=.3141592654D1)
RAD=PI/.18D3
RADI=.18D3/PI
JDEP=.2451545D7
JD=AJDATE(DATE,GMT)
T=(JD-JDEP)/.36525D5
DEP=.46815D2*T+.6D-3*T**.2D1-.181D-2*T**.3D1
EP=.23439292D2-DEP/.36D4
ECLON1=ECLON*RAD
ECLAT1=ECLAT*RAD
EP=EP*RAD
TEMP1=DSIN(ECLAT1)*DCOS(EP)
TEMP2=DCOS(ECLAT1)*DSIN(EP)*DSIN(ECLON1)
DEC=DASIN(TEMP1+TEMP2)*RADI
ANR=DSIN(ECLON1)*DCOS(EP)-DTAN(ECLAT1)*DSIN(EP)
DNR=DCOS(ECLON1)
RA=ATND(ANR,DNR)*RADI
RETURN
END

SUBROUTINE HOCS(DATE,GMT,GLAT,GLON,DEC,RA,ALT,AZI)
IMPLICIT LOGICAL (A-Z)
c IMPLICIT DOUBLE PRECISION (A-Z)
DOUBLE PRECISION GMT,GLAT,GLON,DEC,RA,ALT,AZI,U1,U2,V2
DOUBLE PRECISION PI,RAD,RADI,HANG,HANG1,GLAT1,DEC1
DOUBLE PRECISION HOURANG,ATND
PARAMETER (PI=.3141592654D1)
CHARACTER*15 DATE
RAD=PI/.18D3
RADI=.18D3/PI
HANG=HOURANG(DATE,GMT,GLON,RA)
HANG1=HANG*.15D2*RAD
DEC1=DEC*RAD
GLAT1=GLAT*RAD
U1=DSIN(DEC1)*DSIN(GLAT1)+DCOS(DEC1)*DCOS(GLAT1)*DCOS(HANG1)
ALT=DASIN(U1)*RADI
U2=-DCOS(DEC1)*DSIN(HANG1)*DCOS(GLAT1)
V2=DSIN(DEC1)-DSIN(GLAT1)*DSIN(ALT*RAD)
AZI=ATND(U2,V2)*RADI
RETURN
END

DOUBLE PRECISION FUNCTION GST(DATE,GMT)
IMPLICIT LOGICAL (A-Z)
c IMPLICIT DOUBLE PRECISION (A-Z)
CHARACTER*15 DATE
DOUBLE PRECISION JD,JDEP,T,T0,TT,GST1,GMT,AJDATE
JDEP=.2451545D7
JD=AJDATE(DATE,.0D0)
T=(JD-JDEP)/.36525D5
T0=.6697374558D1+.2400051336D4*T+.25862D-4*T**.2D1
TT=DINT(abs(T0)/.24D2)+.1D1
T0=T0+TT*.24D2
GST1=GMT*.1002737909D1+T0
TT=DINT(GST1/.24D2)
GST1=GST1-TT*.24D2
GST=GST1
RETURN
END

DOUBLE PRECISION FUNCTION ATND(Y,X)
IMPLICIT LOGICAL (A-Z)
c IMPLICIT DOUBLE PRECISION (A-H,O-Z)
DOUBLE PRECISION x,y,pi,dir
PARAMETER (PI=.3141592654D1)
IF (X .EQ. .0D0 .OR.Y .EQ. .0D0) THEN
IF (X .EQ. .0D0 .AND.Y .EQ. .0D0) DIR=.0D0
IF (X .EQ. .0D0 .AND.Y .GT. .0D0) DIR=PI/.2d1
IF (X .EQ. .0D0 .AND.Y .LT. .0D0) DIR=.15D1*PI
IF (Y .EQ. .0D0 .AND.X .GT. .0D0) DIR=.0D0
IF (Y .EQ. .0D0 .AND.X .LT. .0D0) DIR=PI
ELSE
DIR=ATAN(Y/X)
IF (Y .GT. .0D0 .AND.X .LT. .0D0 ) DIR=DIR+PI
IF (Y .LT. .0D0 .AND.X .LT. .0D0 ) DIR=DIR-PI
IF (DIR .LT. .0D0) DIR=DIR+.2D1*PI
END IF
ATND=DIR
RETURN
END

SUBROUTINE GECS(GLAT,GLON,SLAT,SLON,ASAT,ZSAT)
IMPLICIT LOGICAL (A-Z)
c IMPLICIT DOUBLE PRECISION (A-H,O-Z)
DOUBLE PRECISION HSAT,ERAD,PI,GLAT,GLON,SLAT,SLON,ASAT,ZSAT
DOUBLE PRECISION RAD,RADI,GLAT1,GLON1,SLAT1,SLON1,DLAT,DLON
DOUBLE PRECISION U1,V1,U2,V2,ATND
PARAMETER (HSAT=.384d9,ERAD=.6378D7)
c PARAMETER (HSAT=.35786D8,ERAD=.6378D7)
PARAMETER (PI=.3141592654D1)
RAD=PI/.18D3
RADI=.18D3/PI
GLAT1=GLAT*RAD
GLON1=GLON*RAD
SLAT1=SLAT*RAD
SLON1=SLON*RAD
DLAT=(GLAT1-SLAT1)
DLON=(GLON1-SLON1)
U1=(HSAT+ERAD)*DCOS(DLAT)*DCOS(DLON)-ERAD
V1=HSAT**.2D1+.2D1*ERAD*(ERAD+HSAT)*(.1D1-DCOS(DLAT)*DCOS(DLON))
U2=DSIN(DLON)
V2=DCOS(DLON)*DSIN(DLAT)
ASAT=DASIN(U1/SQRT(V1))*RADI
ZSAT=(ATND(U2,V2)+PI)*RADI
IF (ZSAT .GT. .36D3) ZSAT=ZSAT-.36D3
RETURN
END

DOUBLE PRECISION FUNCTION AJDATE(DATE,GMT)
IMPLICIT LOGICAL (A-Z)
c IMPLICIT DOUBLE PRECISION (A-H,O-Z)
DOUBLE PRECISION A,B,C,D,MONTH,JDBC,GMT,DAY,YEAR
PARAMETER (JDBC=.17209945D7)
CHARACTER*15 DATE,INSTR
WRITE(INSTR,100) DATE
100 FORMAT (A15)
READ (INSTR,200) DAY,MONTH,YEAR
200 FORMAT (2(F2.0,1X),F4.0)
DAY=DAY+GMT/.24D2
IF (MONTH .LT. .3D1) THEN
YEAR=YEAR-.1D1
MONTH=MONTH+.12D2
END IF
A=DINT(YEAR/.1D3)
B=.2D1-A+DINT(A/.4D1)
C=DINT(.36525D3*YEAR)
D=DINT(.306001D2*(MONTH+.1D1))
ajdate=b+c+d+day+jdbc
return
end



The Sunglint

Links to sites and software Posted by peter.thejllPosted on Oct 24, 2011 13:47

This IDL code will create a map showing the Earth and the point on the surface where the sunglint travelled, as seen from the Moon, during a specified time interval.

test_sunglint.pro

Look in idl_tools/



Living Planet site

Links to sites and software Posted by peter.thejllPosted on Oct 24, 2011 12:02

Helps visualize the Earth as seen from the Moon at user-selectable times: http://www.fourmilab.ch/cgi-bin/Earth

We need to learn how to use this site for finding the ‘sunglint’ coordinates on Earth. We also should understand if the site can show the actual cloud cover at a given time.