Terminology, controversy, flare, NORAD, altitude, etc.
Walter Nissen (dk058@cleveland.Freenet.Edu)
Sun, 5 Oct 1997 11:26:24 -0400 (EDT)
Jim Varney writes:
> "For the last couple of years on SeeSat I thought the general
> convention was to use the word "glint" to mean any bright, singular
> short-lived flash of reflected sunlight. IMHO "glint" is a more
> precise term than "flare" because it accurately describes the
> mechanism of the flash of light we see.
> "There's no harm in using "flare" except that the Seesat archives are
> full of references to various satellites that "glint" but do not
> "flare." A very minor and trivial point, to be sure, but it's my two
> cents for consistency."
(Jim, can you easily tell me the date you originally posted this?)
English is a hodgepodge language accumulating various inconsistent parts
from numerous sources, with little regard for the needs of technical
communication. Sometimes one sees a tendency to return to the wild and
woolly days before Webster and the OED when spelling and usage were
"creative".
(Summary: English is a mess.)
If we wish to be understood here, with readers coming from various
backgrounds and with various native tongues, we will need to cooperate in
being consistent when consistency is important and in developing a process
to decide how to resolve existing inconsistencies which are troublesome.
Cooperation requires hearing the views of all sides and being willing to
accomodate all views to the maximum extent possible.
(Summary: We can fix it, but only if we want to.)
I have repeatedly expressed what I believe is the essential attitude:
"This is what makes sense to me, for these reasons, but if there is a
movement toward a universal standard which is satisfactory, then I will
adopt the standard whenever reasonably possible".
(Summary: Tell us what you want, then use what people agree to.)
"flash" is the general term meaning that a dark satellite grew brighter.
"glint" is used when there is only one brightening per pass, and suggests
that the brightening might be be due to the changing relationship between
observer and satellite as the satellite moves along its orbit. It serves
the useful purpose of distinguishing being a (presumably) non-rotating
satellite and a (presumably) rapidly rotating one. "specular" is used
when the variation in brightness is so great as to suggest that a
mirror-like surface is reflecting the sun.
(Summary: a glint is a single flash; specular is like a mirror).
As far as I know, "flare" means the astronaut is broken down at the side
of the road, and being safety conscious, wishes to announce that he is
temporarily unable to perform a collision avoidance maneuver. "flare" has
the undesirable characteristic of having the same initial letter as
"flash". In the PPAS, "F" already means "brightening", possibly minor, if
that was all that was seen, and thus is not available to denote "flare",
or something brighter. Flare has an undesirable connotation of activity,
and seems unnecessary because brightnesses have generally been quantified
in the most obvious way, by numbers, and expressed in candela, lumen (or
earlier units) or the highly persistent "magnitude". Where one can sort
of wink at the desirability of quantification by numbers, the exclamation
mark "!" is available to mark a flash as especially bright, or
surprisingly bright.
(Summary: "flare" may not be supported by logic).
The term "altitude" has long been used by astronomers to denote the
complement of the "zenith distance" (a term with its own serious
problems). It is plain in meaning, is used consistently and denotes a
quantity with a continuing usefulness. It seems fully satisfactory in
present-day usage. For these reasons, it seems doubtful that it will
become less important or go into eclipse.
(Summary: "altitude" is here to stay, with its traditional meaning.)
The term "elevation" has long been used by surveyors and geographers to
measure distance above mean sea level. It has readily accommodated the
transition to SI, where it is measured in meter. It is plain in meaning,
is used consistently and denotes a quantity with a continuing usefulness.
It seems fully satisfactory in present-day usage. For these reasons, it
seems doubtful that it will become less important or go into eclipse.
(Summary: "elevation" is here to stay, with its traditional meaning.)
When altitude and azimuth are given together as coordinates of a position
on the celestial sphere, the long-standing practice, as reflected in such
terms as "alt-az mount" is to present the altitude first. This meshes
nicely with the ability to say, e.g., "she will culminate 60 degrees over
270" or "45 degrees above 180". For the sky, altitude measures something
which is above an imaginary circle on the horizon defining azimuth. (As
opposed, I suppose, to directions within a subterranean cave). It seems
internally inconsistent to show the altitude beneath the azimuth, and
needlessly confusing to show the azimuth before the altitude.
(Summary: altitude/azimuth remains the desirable usage).
I don't know the actual history, but it seems that, perhaps earlier in
this century, aeronauts, feeling a need to distinguish between the
elevations of terrestrial features as shown on maps and the elevations of
airships, began referring to elevations of airships as "altitude".
Unfortunately, this term has not proven to be subject to such
appropriation and it now seems the attempt was a mistake. With the
legitimate term "altitude" mis-appropriated for "elevation", it then
seemed necessary to use a different term for "altitude". Someone with a
sense of humor must have suggested compounding the problem by using
"elevation". I can only hope that this was done in the hope that the
situation would then seem so ludicrous and so unsatisfactory, that it
would have to be changed. To me, it still seems so ludicrous and so
unsatisfactory that it should be changed. Normally, persisting in a
mistake is not seen as virtuous.
(Summary: the disadvantges of azimuth/elevation outweigh the advantages).
Alphonse POUPLIER, alphonse.pouplier@skynet.be, writes:
> >>The STSPLUS way is most common (West negative)
> >>The sign agrees with the UTC offset
> There is a recommendation of the International Astronomical Union:
> Longitudes from 0 to 360 deg. EAST
I think the IGU(?), International Geophysical Union(?) and the AGU
recommend essentially the same thing, allowing negatives for the West,
and that there is very general agreement about this. Use of West
longitude is obsolete.
> Who uses it? Almost nobody...
> I do.
Many organizations use East.
(Summary: Use East longitude).
Some astronomical texts measure azimuth from the South, as opposed to the
usual practice of measuring from the North. Aeronauts are consistent here
with usual practice, measuring from North, but they call it "heading" and
sometimes divide by 10 without notice. I am unaware of any organization
which has adopted anything except measurment from the North. The RGO, the
USNO, IOTA, NASA, etc., etc., all seem to use North. Does anyone believe
that there is a serious question here?
(Summary: azimuth should be measured East from North).
Re: Iridia vs. Iridiums (fingernails scraping upon a blackboard):
I've found myself using the abbreviation Irdm, pronunciation "Er dim",
everything swallowed, almost no vowel sounds. Irdms doesn't seem nearly as
objectionable. Also, it is easily pronouncable by 4-year-olds and the
lingually-challenged, should that be seen as important.
(Summary: I propose use of the abbreviation "Irdm", pronounced "Er dim",
plural "Irdms".)
Re: amateur
In astronomical usage, this is an extremely unpleasant word, and should be
avoided in polite company. (Those who are prepared to pay the
psychological price of the very unpleasant, uncensored version of this
paragraph may write to me at dk058@cleveland.freenet.edu).
(Summary: Don't use "amateur". Use "observer", "loser", "taxpayer",
"photographer", "investigator", "stumblebum", "klutz", "citizen", etc., as
appropriate).
The term NORAD seems to have outlived its usefulness. I've noticed that
the catalog which NORAD began, and which US SPACECOM continues, is so
comprehensive that it has shoved away all competitors, so that usually the
term "NORAD catalog number" means no more than the term "catalog number".
Therefore, the general rule is simply to delele the "NORAD". This is good
because "NORAD" is a doubly-troublesome term: it is jargon (possibly an
unfamiliar acronym) and it is now obsolete.
(Summary: don't use "NORAD").
"elements", "elset", "keps", "TLE", and "2LN" are all used to denote the
same thing. Here are 2 I'm using right now:
STS-86 mine
1 24964U 97055A 97277.92229036 .00012129 00000-0 15139-3 0 918x
2 24964 51.6332 254.3229 0018111 5.3881 354.7470 15.67107015 1397
Mir mine
1 16609U 86017A 97277.92662262 .00006372 00000-0 82663-4 0 919x
2 16609 51.6533 254.3462 0006248 179.0518 181.0651 15.60271446664154
"elements" quite frequently is used to mean any set of elements, not
solely the particularly widely-used set known as an "elset". "TLE" and
"2LN" have the overwhelming advantage of fitting in the 3-character
filename extension field. We should probably challenge those who think we
need both "TLE" and "2LN" to justify making a distinction. Absent such a
distinction, we should pick one and use it. Until acronyms become a
pleasant part of the language, people will use words instead, absent a
strong need to the contrary. I think "elset" is a highly desirable term,
because it is pretty obvious in meaning, is more specific than "elements",
is easy to pronounce and scans well. I think I generally use it. I like
it. "keps" and "elements" are awkward because the singular is already
plural.
(Summary: We don't need both TLE and 2LN. Pick one. "elset" is good.)
Kosmos, Cosmos, C*, C, K, C., K., Cos, Ksms, etc., etc. Pick one, and a
useful abbreviation. Stop being silly.
Astronomy is a field with many problems of nomenclature. Formerly solid
distinctions such as those between star and planet, between planet and
asteroid, between comet and asteroid, between planet and satellite,
between satellite and dust are revealed to be tottering and collapsed.
We have no need of artificial, resolvable problems.
(Summary: Big trouble in astronomical "terms").
One of the important reasons for fixing on a unique, unambiguous term for
each concept is that it greatly facilitates the use of search engines.
The prose may not be as "interesting", nor so obviously display the
author's creativity and intelligence, but it will be more easily
understood and more useful.
(Summary: Pick one, unambiguous term and always use it).
Perfection is unachievable. The best is enemy of the good.
I would hope that those of us who care about these issues would make known
all legitimate points of view; expressing all arguments with a view toward
resolving problems and achieving consensus; be determined to achieve a
consensus if possible, even if that means giving up a current usage; and
be determined to adopt emerging standards in widespread use.
(Summary: Let's fix these problems, respecting different ideas, and using
logic to resolve the inconsistencies.)
Please feel free to reproduce this message, and its call for discussion,
in any other appropriate forum, such as sci.astro (Jay?),
sci.space.policy, etc.
Cheers.
Walter Nissen dk058@cleveland.freenet.edu
-81.8637, 41.3735, 256m elevation
---
New Baseball Terminology (quoted from this week's "Baseball Weekly", while
withholding judgment as to accuracy and appropriateness):
Albertross = Paying $55 million for a guy who *does* hit, but still manages
to bring your team *down* ... choke.
---
Power corrupts. Absolute power corrupts absolutely. Lord Acton