Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Wed, 11 Jul 1990 01:50:40 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Wed, 11 Jul 1990 01:50:09 -0400 (EDT) Subject: SPACE Digest V12 #44 SPACE Digest Volume 12 : Issue 44 Today's Topics: Ray tracing and optical simulation... Re: NASA's lobbying on the net Re: Investing in NASA Re: SPACE Digest V12 #38 Re: grim tidings for the future Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription notices, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 10 Jul 90 22:08:09 GMT From: skipper!bowers@ames.arc.nasa.gov (Al Bowers) Subject: Ray tracing and optical simulation... Hi folks, With all this talk about optical simulation and aberrations I thought I'd dig up an old program that I had. I got this from Sky & Telescope, April 1981. The original is in BASIC, but as most of the machines I work on are FORTRAN literate, I made the conversion. It only works for parallel rays to the axis prior to the entrance pupil. The example given is for a Schmidt corrector Cassegrain camera (see the above mentioned issue of S&T). Now all I need is a descrption of a Ritchey-Chretien and we (here on the net) can bastardize it to see how badly we (NASA) `screwed the pooch'. The example input and output follows the program. ============================================================================= program ray c ... ray trace program c ... c ... algorithm from Sky and Telescope, April 1981 c ... fortran conversion by Al Bowers, Jul 06, 1990 c ... c ... ep ray ht = entrance pupil ray height c ... ep-s3 dist = entrance pupil to surface 3 distance c ... k5 = 0, new optical system c ... <> 0, uses the previously entered optical system c ... c ... cv = curvature, reciprocal of the radius c ... th = thickness or air space c ... index = refractive index for the wavelength of light c ... skode = surface code c ... = -1, for a plane c ... = 0, spherical c ... = 1, aspheric, program will ask for more if selected c ... surfn0 = surface number c ... c ... conc = conic constant c ... > 0, oblate spheroid c ... = 0, sphere c ... = 0>-1, ellipsoid c ... = -1, parabola c ... < -1, hyperboloid c ... asph4,6,8,10 = coefficients of even powers of distance from optic axis c ... dimension l(20,8),k(20),y(20) real l,l1,l2,m1,m2 do 80 i=1,2 do 60 j=1,8 l(i,j)=0 60 continue k(i)=0 80 continue l(1,3)=1 l(2,3)=1 100 print(6,*) 'enter ep ray ht, ep-s3 dist, and k5' read(5,*) y(2),l(2,2),k5 if(k5.ne.0) goto 260 print(6,*) 'enter cv, th, index, skode, surfn0' do 230 i=3,20 read(5,*) l(i,1),l(i,2),l(i,3),k(i),s1 if(k(i).le.0) goto 200 print(6,*) 'enter conc, asph4,6,8,10' read(5,*) l(i,4),l(i,5),l(i,6),l(i,7),l(i,8) if(l(i,4).le.0) goto 200 l(i,4)=l(i,4)-1 200 if(s1.ne.0.) goto 230 l5=i c ... l5 = last surface number goto 240 230 continue 240 if(l(3,3).eq.0) goto 1160 do 250 m=1,l5 245 l(m,4)=l(m,4)+1 250 continue 260 k(i)=-1 k(2)=-1 l(1,2)=1.000000e+20 y(1)=0 y2=y(2) z=0 m2=1 t1=0 m1=1/sqrt(1+t1*t1) l1=t1*m1 g1=m1 j=2 360 d=(l(j,2)-z)/m1 y1=y2+l1*d j=j+1 if(k(j).ge.0) goto 460 y2=y1 z=0 l2=z m2=1 g3=m1 goto 850 460 t1=l(j,1)*(1+(l(j,4)-1)*m1*m1) t2=m1-l(j,1)*y1*l1 t3=l(j,1)*y1*y1 t4=t2*t2-t1*t3 if(t4.le.0.) goto 1070 g3=sqrt(t4) if(t2.ge.0.) goto 540 g3=-1.*g3 540 d1=t3/(t2+g3) y2=y1+l1*d1 z=m1*d1 if(k(j).lt.0) goto 850 if(k(j).eq.0) goto 830 m2=1 i=0 610 t1=y2*y2 t2=1-l(j,4)*l(j,1)*l(j,1)*t1 if(t2.le.0.) goto 1090 t3=sqrt(t2) t4=l(j,1)/(1+t3) t5=l(j,1)/t3 s=z-((((l(j,8)*t1+l(j,7))*t1+l(j,6))*t1+l(j,5))*t1+t4)*t1 f=(((10*l(j,8)*t1+8*l(j,7))*t1+6*l(j,6))*t1+4*l(j,5))*t1 f=f+t5 l2=-1.*(y2*f) g3=l2*l1+m1 d1=d1-s/g3 y2=y1+l1*d1 z=m1*d1 t6=abs(s) if(t6.le.1.0000e-07) goto 850 i=i+1 if(i.le.1000) goto 610 790 print(6,*)'aspheric test failed in trace ',k2 goto 1160 t1=y2*y2 y(j)=y2 830 l2=-1.*l(j,1)*y2 m2=1-l(j,4)*l(j,1)*z 850 t1=y2*y2 y(j)=y2 if(j.eq.l5) goto 1110 g2=l2*l2+m2*m2 r1=l(j-1,3)/l(j,3) if(r1.ge.0.) goto 950 g1=-1.*g3/g2 r=1. g4=g1+g1 goto 1040 950 r=r1 t1=r*g3/g2 t2=(r*r-1)/g2 t3=t1*t1-t2 if(t3.le.0.) goto 1090 g1=sqrt(t3) if(t1.ge.0.) goto 1030 g1=-1.*g1 1030 g4=g1-t1 1040 l1=r*l1+g4*l2 m1=r*m1+g4*m2 goto 360 1070 k2=-1.*j goto 790 1090 k2=j goto 790 1110 print(6,*) 'curvature thickness index y' do 1140 i=2,l5 print(6,1130) l(i,1),l(i,2),l(i,3),y(i) 1130 format(4f14.7) 1140 continue goto 100 1160 stop end ============================================================================= Following is a sample run. The lines that are typed in by the user (_YOU_) are followed by a `<='. All others are from the program. To terminate the run simple type in zeros for all prompted inputs. ============================================================================= enter ep ray ht, ep-s3 dist, and k5 107.39 0 0 <= enter cv, th, index, skode, surfn0 .00005807 9.525 1 3 <= enter conc, ashp4,6,8,10 0 -1.87279e-09 -7.97425e-15 3.13145e-21 0 <= 0 536.43 1 -1 4 <= -.00181663 -149.123 -1 1 5 <= enter conc, ashp4,6,8,10 1.0943768 0 0 0 0 <= -.00181663 225.864 1 0 6 <= 0 0 1 -1 0 <= curvature thickness index y .0000000 .0000000 1.0000000 107.3899990 .0000581 9.5249996 1.4632000 107.3899990 .0000000 536.4299920 1.0000000 107.4011300 -.0018166 -149.1230010 -1.0000000 108.3070670 -.0018166 225.8639980 1.0000000 49.6727600 .0000000 .0000000 1.0000000 .0064888 enter ep ray ht, ep-s3 dist, and k5 85 0 1 <= curvature thickness index y .0000000 .0000000 1.0000000 85.0000000 .0000581 9.5249996 1.4632000 85.0000000 .0000000 536.4299920 1.0000000 84.9996337 -.0018166 -149.1230010 -1.0000000 84.9692001 -.0018166 225.8639980 1.0000000 38.8188095 .0000000 .0000000 1.0000000 -.0022316 enter ep ray ht, ep-s3 dist, and k5 60 0 2 <= curvature thickness index y .0000000 .0000000 1.0000000 60.0000000 .0000581 9.5249996 1.4632000 60.0000000 .0000000 536.4299920 1.0000000 59.9945297 -.0018166 -149.1230010 -1.0000000 59.5428047 -.0018166 225.8639980 1.0000000 27.1187400 .0000000 .0000000 1.0000000 -.0025940 enter ep ray ht, ep-s3 dist, and k5 0 0 0 <= enter cv, th, index, skode, surfn0 0 0 0 0 0 <= ============================================================================= Just thought it might be of interest. Another opinion... -- Albion H. Bowers bowers@elxsi.dfrf.nasa.gov ames!elxsi.dfrf.nasa.gov!bowers ------------------------------ Date: 10 Jul 90 02:14:59 GMT From: bfmny0!tneff@uunet.uu.net (Tom Neff) Subject: Re: NASA's lobbying on the net I wish I could agree with Nick on this, but a lot of the stuff that could be considered pro-NASA lobbying from people at Lewis, Ames etc, also contains bits of information (sometimes carefully selected!) about what's going on, and I would hate to lose that. One might like to be able to say "only factual postings you humps," but in practice I think NASA people would just clam up completely, and that'd be no fun. Also keep in mind that many of the non-NASA postings are from places, like observatories, that do NASA related work -- are they wrong too? I'm afraid that if we removed ALL interested parties from the debate, and boiled the active membership down to the usual collection of Silicon Valley net-gnomes and Waco, Texas hobbyists, the fun would be gone. Go look at CompuServe SPACEFORUM some time. "A Libertarian Space Program, Part 17 of 29, by Luigi Guacamole Jr." "DERE SYSOP I HERD THAT HUBLE WAS HIT BY A UFO??" "Hubble So-called 'Defect' a Communist Media Conspiracy?" etc. Real enlightening stuff. So, although I wish some of these people would take a break from the net and use the time to finish remedial 6th grade spelling, on the whole I want to hear from EVERYONE, including people at NASA. The ones who aren't afraid to take up the cudgels for the agency in *this* crowd are actually the good guys. It's the silent paper pushers I worry about. -- "Just when we finally got good at this, we \_i_/ Tom Neff run out of planets." - a Voyager scientist --[o]-- tneff@bfmny0.BFM.COM ------------------------------ Date: 10 Jul 90 12:38:16 GMT From: usc!samsung!umich!umeecs!itivax!vax3.iti.org!aws@ucsd.edu (Allen W. Sherzer) Subject: Re: Investing in NASA In article <721.2698F7A2@ofa123.fidonet.org> David.Anderman@ofa123.fidonet.org (David Anderman) writes: >If investing NASA is not a good idea, where should we invest? SSI Allen | | In War: Resolution | | Allen W. Sherzer | In Defeat: Defiance | | aws@iti.org | In Victory: Magnanimity | | | In Peace: Good Will | ------------------------------ From: AZM@CU.NIH.GOV Date: Tue, 10 Jul 90 10:46:55 EDT Subject: Re: SPACE Digest V12 #38 > >And another thing, HST has not failed!!!!!!!! I am tired of hearing > >this. We have every reason to beleive in the end most if not all > >of the science will be done. > And I am tired of the people who keep defending the HST, and protecting whoever is responsible for what happened (just what did happen? did any- thing actually happen?). The HST was supposed to provide VISUAL images of the universe of a kind, and at a resolution of detail, never before seen by man on Earth. NOBODY on the ground really gives a damn about all of the esoteric science that is going to get done (is it realy going to get done? can the instruments really make use of sloppy, fuzzy, shaky images?). I mean NOBODY from among the general public. They wanted to see spectacular new images of galaxies, distant stars, perhaps even "hot planets." Instead, they are going to see nothing. And they are gonna be pissed. They are going to scream bloody murder before they allow any more money to be "thrown away on space garbage." Hmmm? Perhaps the Hubble did succeed after all, if its real purpose was to ring the death knell for civilian NASA. Or perhaps Hubble really is just a third generation "KH"-type spy satellite, and it is up there right now working away just the way it was supposed to, and all the astro-science bull was just a smokescreen. After all, with all of the stupid things that we the people have been told went wrong with the $1.5 billion project, even the credulity of the 10-year-olds in this coun- try is being strained to the breaking point. Hell, even 10-year-olds in rocket clubs around the country wouldn't have overlooked the things that the high-level engineers and scientists at the Hubble-bubble are suppos- ed to have overlooked. And now they're trying to sell the idea that the Hubble "might" get fixed in mid-1993, or if that "don't get it" then in 1996. Does anybody at the Hubble-bubble really expect the american "live-for-the-micro- second public to sit still and wait three or even six years for the fix to go up. It is to laugh. AZM@NIHCU ------------------------------ Date: 10 Jul 90 16:29:06 GMT From: hao.hao.ucar.edu!dlb@handies.ucar.edu (Derek Buzasi) Subject: Re: grim tidings for the future In article <37486@ucbvax.BERKELEY.EDU> gwh@OCF.Berkeley.EDU (George William Herbert) writes: #In article <7315@timbuk.cray.com> gbt@sequoia.cray.com (Greg Titus) writes: #> #>Doesn't matter what they call it. They're all experimental. #>By the time the entire shuttle program is ended, the SMEs will #>still not have been run for as much aggregate time as the #>engines on a Boeing 747 on a *single* New York to Tokyo round #>trip. Experience with the things NASA flies was, is and will #>remain for a long time very limited compared with what we know #>about more mundane objects. # #While I agree in general, your example is in error... The engines run #8 minutes each in a flight, or 24 engine-minutes. With the testing that is #run outside of flights, there are about three times as many off-flight engine #hours as on-flight, or about 96 engine-minutes (1.5 engine-hours) per flight. #This totals to about fifty flight hours so far, and with fifty to a hundred #shuttle flights ahead, another seventy five to one hundred fifty hours of #operation. # #Now, while a 747 has four engines, i doubt that it takes 25 hours to fly #from New York to Tokyo... # #-george Ah, but round trip, like the man said? -- ****************************************************************************** Derek Buzasi * "History is made at night. High Altitude Observatory * Character is what you are in the dark." dlb@hao.ucar.edu * -- Lord John Whorfin ------------------------------ End of SPACE Digest V12 #44 *******************