NEW QUANTITY @name DESCRIPTION (1:)@word
(0:4){ FORMAT (1:)@word
| UNITS @word
| HEADING (1:)@word
| NO LEGEND }
Optional Syntax:
NEW! QUANTITY @name DESCRIPTION (1:)@word
(0:4){ FORMAT (1:)@word
| UNITS @word
| HEADING (1:)@word
| NO LEGEND }
The NEW QUANTITY command is used to name a quantity that can then be used as
part of a report or FIND command. Quantities have 5 parts: a name, a
description, formatting information, an optional heading and an option to
preclude this quantity from showing up in a legend for any report that might
include this quantity.
If you specify a quantity using the NEW QUANTITY version of this command, for a quantity that has already been named, PERCY will not overwrite the existing quantity. Instead you will be informed that you are duplicating a quantity name and the command will have no effect. If you really want to overwrite an existing quantity you have two options:
Every QUANTITY has a descriptive clause that describes the value associated
with the quantity. This clause is the
DESCRIPTION (1:)@wordportion of the NEW QUANTITY command. In addition, every quantity has associated with it a print format and units in which it may be displayed. These are specified through the optional FORMAT and UNITS clauses given in the syntax description. Syntactic descriptions of all available quantities, allowed units and formats are given below.
The time quantity is used to have times associated with other quantities
appear in reports. The description for the time quantity is very simple.
TIME FORMAT @systemUnits are ignored in the TIME quantity as they are included in the FORMAT description. Acceptable systems to supply as time format are: UTC, DOY, JED, JDUTC, and SP2000TDB (seconds past the ephemeris epoch J2000 TDB).
In addition to these predefined formats for time output, PERCY allows you to create your own format as well as select any of the time systems: TDB, TDT or UTC. To do this you supply a ``picture'' that represents how time should be portrayed. In this case the TIME description takes the form:
TIME FORMAT @pictureFor example, the format picture
YYYY-DOY.HR:MN:SC.###produce time strings such as
1992-231.12:18:57.221A more complete discussion of formatting time strings is provided in the chapter About Time Formats.
A number of angular quantities may be specified as entries. You may supply
either a picture for the output of these angles
Picture format has the form such as xxx.xxxxx.
The units specified must be appropriate angular units or angular rate units.
ANGULAR RATE OF @body FROM @obs RELATIVE @body APPARENT DIAMETER OF @body FROM @obs ELONGATION OF @body FROM @obs PHASE OF @body FROM @obs SEPARATION OF @body @body FROM @obs FORMAT @fmt UNITS @units
A number of quantities are available that yield the distances between solar
system bodies and designated objects. Formats should be picture formats.
Units must be appropriate distance and distance rate units.
DISTANCE BETWEEN @body @body FROM @obs DISTANCE OF @body FROM @obs DISTANCE RATE BETWEEN @body @body FROM @obs DISTANCE RATE OF @body FROM @obs FORMAT @fmt UNITS @units
All of the basic inertial coordinates and their derivatives are available for
use as quantities. Allowed coordinates are: X, Y, Z, RA (right ascention),
DEC (declination) and RANGE. The derivatives of these quantities are
specified by: DX, DY, DZ, DRA DDEC and DRANGE respectively. Picture formats
are used to specify the format. Units must be appropriate for the coordinate
specified.
FRAME @name @coordinate OF @body FROM @obs FORMAT @fmt UNITS @units
The following quantities allow you to retrieve position angles of one object
relative to another as seen from a specified observation point. Formats
should be picture formats. Units must be angular units.
NORTH POSITION ANGLE OF @body FROM @obs RELATIVE @body SOLAR POSITION ANGLE OF @body FROM @obs RELATIVE @body FORMAT @fmt UNITS @unitsThe syzygy quantities are ``boolean'' quantities. They either are not or are in the condition specified. Formats are specified by concatenating a marker character (implied by the first character of the format word) followed by a ``not in state'' string. This is followed by the marker character and the ``in state'' string. For example a possible format for the occultation quantity would be
FORMAT "-Visible-Occulted"The marker character in this case is the hyphen ``-''. When the objected specified is not occulted the word ``Visible'' would be used to report the value of the quantity. When the object is occulted, the word ``Occulted'' would be used to report its value.
OCCULTATION OF @body BY @body FROM @obs TRANSIT OF @body ACROSS @body FROM @obs ECLIPSE OF @body BY @body FROM @obs PENUMBRAL ECLIPSE OF @body BY @body FROM @obs UMBRAL ECLIPSE OF @body BY @body FROM @obs FORMAT @no-yes
The following quantities allow you to determine body-fixed positions of one
object relative to another as seen from a third.
CENTRAL MERIDIAN LONGITUDE OF @body FROM @obs CARTOGRAPHIC @coordinate OF @body RELATIVE @body FROM @obs PLANETOCENTRIC @coordinate OF @body RELATIVE @body FROM @obs PLANETOGRAPHIC @coordinate OF @body RELATIVE @body FROM @obs FORMAT @fmt UNITS @unitsFor Cartographic and Planetocentric entries, acceptable coordinates are: LATITUDE, LONGITUDE, RADIUS, LATITUDE RATE, LONGITUDE RATE, RADIUS RATE. For Planetographic entries, acceptable coordinates are: LATITUDE, LONGITUDE, HEIGHT, LATITUDE RATE, LONGITUDE RATE, HEIGHT RATE. Units for latitude and longitude must be angular. For radius and height, units must be units of distance. Rate quantities must be angular rates and distance rates respectively. Formats must be picture formats.
Orbital longitude entries return the orbital longitude of a body relative to its center of motion. The syntax for this quantity is
ORBITAL LONGITUDE OF @body FROM @obs FORMAT @fmt UNITS @unitsFormats should be picture formats. Units must be angular units.
When you create a new quantity you specify a name that you can then use to
refer the quantity later in your PERCY session. However, this name may not be
what you care to have appear in a report heading when the quantity it appears
in a report. For this reason you may create a more suitable heading for this
quantity using the optional
HEADING (1:)@wordclause of the NEW QUANTITY command. Your heading must be limited to 32 or fewer characters.
Quantities support the GENERATE REPORT facility of PERCY. When a report is
generated, you may specify that a "legend" be printed at the top of the first
page of the report. The legend describes the various entries appearing in the
report. However, the meaning of an item may be clear from the heading you
have selected for a quantity. In such a case, you may prefer to save space on
the first page by not including the quantity description in the report's
legend, thus keeping the legend smaller and allowing more room for
data-lines. To do this include the
NO LEGENDclause in your new quantity definition. By doing so you ensure that any report referring to this quantity will not include a description of the quantity in the report legend.
Here is how you could create a report that gives the right ascesion,
declination and elongation of Mars as a function of time.
NEW QUANTITY TIME DESCRIPTION TIME FORMAT UTC HEADING "Time" NO LEGEND;
NEW QUANTITY ELONG DESCRIPTION ELONGATION OF MARS FROM EARTH
FORMAT XXXXXXXXX.XX UNITS DEGREES
HEADING "Elongation of Mars";
NEW QUANTITY RA DESCRIPTION FRAME J2000 RA OF MARS FROM EARTH
FORMAT XXX.XXXX UNITS DEGREES
HEADING "R.A.";
NEW QUANTITY DEC DESCRIPTION FRAME J2000 DEC OF MARS FROM EARTH
FORMAT XXX.XXXX UNITS DEGREES
HEADING "Dec.";
NEW REPORT MARS_DATA ENTRIES TIME ELONG RA DEC;
GENERATE SMART REPORT MARS_DATA FROM 1 JAN 1991 TO 1 DEC 1991
EVERY 2 WEEKS HEADER LEGEND;
The resulting report would look like this:
Elongation of Mars --- ELONGATION OF 4 FROM 399 FORMAT
XXXXXXXXXX.XX UNITS DEGREES
R.A. --- J2000 RIGHT ASCENSION OF 4 FROM 399
FORMAT XXX.XXXX UNITS DEGREES
Dec. --- J2000 DECLINATION OF 4 FROM 399 FORMAT
XXX.XXXX UNITS DEGREES
Corrections for Stellar aberration are enabled.
Time Elongation of R.A. Dec.
(utc) Mars (degrees) (degrees)
(degrees)
===================================================================
1991 JAN 01 00:00:00.0 137.37 55.0480 21.9656
1991 JAN 15 00:00:00.0 124.23 56.1913 22.2655
1991 JAN 29 00:00:00.0 113.15 59.5303 22.9024
1991 FEB 12 00:00:00.0 103.61 64.5064 23.6961
1991 FEB 26 00:00:00.0 95.20 70.6984 24.4673
1991 MAR 12 00:00:00.0 87.64 77.7730 25.0608
1991 MAR 26 00:00:00.0 80.71 85.4918 25.3570
1991 APR 09 00:00:00.0 74.28 93.6486 25.2694<
1991 APR 23 00:00:00.0 68.24 102.0850 24.7425
1991 MAY 07 00:00:00.0 62.53 110.6585 23.7505
1991 MAY 21 00:00:00.0 57.07 119.2652 22.2909
1991 JUN 04 00:00:00.0 51.83 127.8227 20.3835
1991 JUN 18 00:00:00.0 46.77 136.2862 18.0612
1991 JUL 02 00:00:00.0 41.85 144.6339 15.3698
1991 JUL 16 00:00:00.0 37.05 152.8740 12.3594
1991 JUL 30 00:00:00.0 32.34 161.0326 9.0869
1991 AUG 13 00:00:00.0 27.70 169.1546 5.6101
1991 AUG 27 00:00:00.0 23.12 177.2969 1.9915
1991 SEP 10 00:00:00.0 18.58 185.5263 -1.7037
1991 SEP 24 00:00:00.0 14.08 193.9168 -5.4040
1991 OCT 08 00:00:00.0 9.61 202.5447 -9.0311
1991 OCT 22 00:00:00.0 5.18 211.4876 -12.4972
1991 NOV 05 00:00:00.0 0.79 220.8132 -15.7039
1991 NOV 19 00:00:00.0 3.01> 230.5768 -18.5434