Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V09_5/V9_596.TXT

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Date: Fri, 11 Aug 89 00:24:30 -0400 (EDT)
Subject: SPACE Digest V9 #596

SPACE Digest                                      Volume 9 : Issue 596

Today's Topics:
      Geosync Satellite Finder (was Re: NASA Select Broadcasts)
            Re: Ground the DC-10!?
         Re: Request for more info on ozone depletion
----------------------------------------------------------------------

Date: 25 Jul 89 10:11:17 GMT
From: mcvax!ukc!reading!cf-cm!cybaswan![e-mail]  (Steve Hosgood)
Subject: Geosync Satellite Finder (was Re: NASA Select Broadcasts)

In article <[e-mail]> [e-mail] (54317-T.EBERSOLE) writes:
>I told a friend of mine about the NASA Select broadcasts of Neptune
>images on Tuesdays at noon. He has looked for them a couple of times
>and had another friend look a couple of times, with no luck picking
>up a signal. He has looked at other times to see if he can get anything,
>also with no luck. Has anyone been able to find NASA Select's broadcasts?
>
>Thanks for any information.
>

Please - before you flame me for this: I *know* sci.space isn't the place
for sources, but I couldn't think of a better place for this one, and it's
not too long anyway. Just copy the rest of this posting into a file, make
it executable and run it as a shell-script. That gives you the file 'geosync.c'
which you compile and run. Enjoy!

CUT HERE --- CUT HERE
if test -f geosync.c; then echo "File geosync.c exists"; else
echo "x - extracting geosync.c (Text)"
sed 's/^X//' << 'SHAR_EOF' > geosync.c &&
X/*
X * GEOSYNC.C - Calculate position of a geostationary satellite.
X * Version 1.2:    S.Hosgood, May 10th 1989
X *
X * This program is in the Public Domain.
X * It may be freely copied and distributed as long as no charge is made.
X *
X * No responsibility can be accepted for the accuracy of the results.
X * The program is for amusement only.
X *
X * Written for the IBM PC, using Microsoft C 4.0.
X * Use is made of the IBM's 'degrees' symbol. It should be no problem to
X * make it work on other systems though
X *
X * To run: just type 'geosync' and answer the questions.
X *
X * Please forward bug reports to:
X * Steve Hosgood ([e-mail]).
X *
X */
X
X# include    <stdio.h>
X# include    <math.h>
X# include    <ctype.h>
X
X# ifndef    PI
X# define    PI        3.141592653589793
X# endif
X
X# define    degtorad(x)    ((x)*PI/180.0)
X# define    radtodeg(x)    ((x)*180.0/PI)
X
X/* Radius of Earth, and Radius of Geosync Orbit */
X/* These constants are off the top of my head, may be a bit wrong */
X# define    E_RAD        6378.388    /* Km (equator) */
X# define    O_RAD        42240.31    /* Km (from centre of earth) */
X
X/* flattening factor for geoid */
X# define    FLAT        (1.0 / 298.26)
X
Xdouble readval( char * );
X
Xmain()
X{
X    double    a, b, c, d, n, w;
X    double    vert, tmp, e_rad;
X    double    satwest, obswest, obsnorth;
X
X    satwest = readval("Enter satellite's Longitude");
X    obswest = readval("Enter observer's Longitude");
X    obsnorth = readval("Enter observer's Latitude");
X
X    a = sin(w = degtorad(satwest - obswest));
X    b = sin(n = degtorad(obsnorth));
X    c = cos(w);
X    d = cos(n);
X
X    /* Earth's radius follows a sin-squared law with latitude (appx) */
X    e_rad = E_RAD*(1 - FLAT*b*b);
X    vert = O_RAD*c*d - e_rad;
X
X    /* attempt to avoid DOMAIN errors from trig functions */
X    if ((tmp = O_RAD*sqrt(c*c*b*b + a*a)) <= 1e-6 && tmp >= -1e-6) {
X        if (vert > 0.0)
X            printf("Vertically up\n");
X        else
X            printf("Vertically down\n");
X    }
X    else {
X        printf("Elevation = %6.2f\370\n", radtodeg(atan2(vert, tmp)));
X
X        if ((tmp = c*b) <= 1e-6 && tmp >= -1e-6)
X            /* bearing directly east or west */
X            tmp = a > 0.0? 90.0: -90.0;
X        else
X            tmp = radtodeg(atan2(a, tmp));
X
X
X        printf("Bearing ");
X        if (tmp > 89.95 && tmp < 90.05)
X            printf("due West");
X        else if (tmp < -89.95 && tmp > -90.05)
X            printf("due East");
X        else {
X            /* nice to see bearings +/- South or +/- North */
X            printf("(Clockwise from ");
X
X            if (tmp < -90.0 || tmp > 90.0) {
X                tmp += 180.0;
X                printf("north");
X
X                if (tmp >= 180.0)
X                    tmp -= 360.0;
X            }
X            else
X                printf("south");
X
X            printf(") = %6.2f\370", tmp);
X        }
X
X        putchar('\n');
X    }
X
X    if ((d = e_rad/(O_RAD*cos(n))) > 1.0 || d < -1.0) {
X        printf("No geosync satellites visible from there\n");
X        printf("Limit latitude is appx \361%6.2f\370\n", radtodeg(acos(E_RAD/O_RAD)));
X    }
X    else {
X        c = radtodeg(acos(d));
X
X        fputs("Satellites ", stdout);
X        prlong(c+obswest);
X        fputs(" thru ", stdout);
X        prlong(obswest-c);
X        fputs(" are visible\n", stdout);
X    }
X
X    exit(0);
X}
X
Xdouble
Xreadval(str)
Xchar *str;
X{
X    char        buffer[30];
X    register char    chr, *cptr;
X    int        err;
X    static        longmesg = 0;
X    double        ret, atof( char * );
X
X    do {
X        /* prompt */
X        fprintf(stderr, "%s: ", str);
X        err = 0;
X
X        cptr = fgets(buffer, sizeof buffer, stdin);
X        if (*cptr == '-')
X            cptr++;
X
X        /* check that a number is present at all */
X        if (!isdigit(*cptr) && *cptr != '.')
X            goto error;
X
X        /* get integer degrees part anyway */
X        ret = atoi(cptr);
X
X        /* look for next non-numeric */
X        for (; (chr = *cptr) && isdigit(chr); cptr++);
X
X        if (chr == ':') {
X            /* get integer of minutes of arc */
X            ret += atoi(++cptr) / 60.0;
X
X            /* step past minutes of arc */
X            for (; (chr = *cptr) && isdigit(chr); cptr++);
X
X            if (chr == ':') {
X                /* get seconds of arc */
X                ret += atof(++cptr) / 3600.0;
X
X                /* step past seconds of arc */
X                for (; (chr = *cptr) && isdigit(chr); cptr++);
X                if (chr == '.')
X                    /* step past optional decimal part */
X                    for (cptr++; (chr = *cptr) && isdigit(chr); cptr++);
X            }
X            else if (chr == '.') {
X                /* get decimal part of minutes of arc */
X                ret += atof(cptr) / 60.0;
X
X                /* step past decimal part */
X                for (cptr++; (chr = *cptr) && isdigit(chr); cptr++);
X            }
X
X        }
X        else if (chr == '.') {
X            /* get decimal part of degrees */
X            ret += atof(cptr);
X
X            /* step past decimal part */
X            for (cptr++; (chr = *cptr) && isdigit(chr); cptr++);
X        }
X
X        /* check final character */
X        switch (chr) {
X        case 'N':
X        case 'n':
X        case 'W':
X        case 'w':
X        case '\n':
X            /* do nothing */
X            break;
X
X        case 'E':
X        case 'e':
X        case 'S':
X        case 's':
X            ret = -ret;
X            break;
X
X        default:
X        error:
X            /* print a fairly useful error message */
X            fputs(buffer, stderr);
X            *cptr-- = '\0';
X            while (cptr >= buffer)
X                *cptr-- = ' ';
X
X            fprintf(stderr, "%s^-----Error in input\n\n", buffer);
X            err = 1;
X        }
X
X        if (err & !longmesg) {
X            fprintf(stderr, "Format: {-}<deg>{NSEW}\n");
X            fprintf(stderr, "<deg> ::= integer or real\n\n");
X            fprintf(stderr, "Or..  : {-}<deg>:<min>{NSEW}\n");
X            fprintf(stderr, "<deg> ::= integer\n");
X            fprintf(stderr, "<min> ::= integer or real\n\n");
X            fprintf(stderr, "Or..  : {-}<deg>:<min>:<sec>{NSEW}\n");
X            fprintf(stderr, "<deg> ::= integer\n");
X            fprintf(stderr, "<min> ::= integer\n");
X            fprintf(stderr, "<sec> ::= integer or real\n\n");
X            fprintf(stderr, "Items in braces are optional\n\n");
X            longmesg++;
X        }
X    } while (err);
X
X    return (*buffer == '-')? -ret: ret;
X}
X
Xprlong(val)
Xdouble val;
X{
X    char    eastwest;
X
X    /* get into range +180 -> -180 degrees */
X    while (val > 180.0)
X        val -= 360.0;
X
X    while (val < -180.0)
X        val += 360.0;
X
X    if (val < 0.0) {
X        eastwest = 'E';
X        val = -val;
X    }
X    else if (val > 0.0)
X        eastwest = 'W';
X    else
X        eastwest = ' ';
X
X    printf("%5.1f\370%c", val, eastwest);
X    return;
X}
SHAR_EOF
chmod 0644 geosync.c || echo "restore of geosync.c fails"
fi
exit 0

-----------------------------------------------+------------------------------
Steve Hosgood BSc,                             | Phone [phone]
Image Processing and Systems Engineer,         | Fax [phone]
Institute for Industrial Information Techology,| Telex 48149
Innovation Centre, University of Wales, +------+ JANET: [e-mail]
Swansea SA2 8PP                         | UUCP: ..!ukc!cybaswan.UUCP!iiit-sh
----------------------------------------+-------------------------------------
            My views are not necessarily those of my employers!

------------------------------

Date: 28 Jul 89 18:29:05 GMT
From: att!laidbak![e-mail]  (Jonathan E. Quist)
Subject: Re: Ground the DC-10!?

In article <[e-mail]> [e-mail] (Bruce Watson) writes:
>
>Why not?  There were civilians aboard.

Did I miss something?

------------------------------

Date: 28 Jul 89 16:35:28 GMT
From: ginosko!aplcen!haven!adm!smoke![e-mail]  (Irving Chidsey )
Subject: Re: Request for more info on ozone depletion

In article <[e-mail]> [e-mail] (John E Van Deusen III) writes:
<I read today in my home-town paper that "scientists" had presented
<"evidence" that the antarctic ozone hole might be "related to" increased
<incidence of skin cancer in southern Australia and New Zealand.  Does
<anyone know anything about this "study"?  It defies logic for a number
<of reasons and is apparently the "first" study to make such a claim.
<--
<John E Van Deusen III, PO Box 9283, Boise, ID  83707, [phone]
<
<uunet!visdc!jiii

There are several plausible reasons why the Antarctic Ozone Hole might have
an effect in Southern Australia or Souther New Zealand.

The hole is not a neat hole with straight vertical sides like you might make
with a drill; it has messy sloping sides like a hole in dry sand after it has
been walked through a few times.

Horizontal winds can move the ozone depleted air for quite a distance before
it gets to a location where the solar UV flux is strong enough to replenish
the ozone.

The ozone density is the result of a dynamic balance between production and
depletion.  The full equilibrium density as approached asymptoticaly, and
extra solar UV gets through until full density is reached.

Note also that they said might.  This is still a conjecture supported by
plausible armwaving arguments, and refuted by other plausible armwaving
arguments.  It sounds like it would be a good learning project for a Phd
candidate ( or perhaps a small group of graduate students ).

                    Irv


--
I do not have signature authority.  I am not authorized to sign anything.
I am not authorized to commit the BRL, the DOA, the DOD, or the US Government
to anything, not even by implication.
            Irving L. Chidsey  <[e-mail]>

------------------------------

End of SPACE Digest V9 #596
*******************