institutionalized confusion, ephemeris server, sample size
Walter Nissen (dk058@cleveland.Freenet.Edu)
Tue, 31 Dec 1996 08:11:55 -0500 (EST)
palmer@sfu.ca (Leigh Palmer) writes:
> Subject: Re: Mir seen at -0.8 degree?
> To: tomnagy@nauticom.net (tom)
> At 8:41 AM 12/29/96, tom wrote:
> >What elevation do you have set for your location?
> and for the elevation of the plains east of the Front Range
> which presumably lie on your horizon? I understand you are
> observing from Colorado.
...
> [Ron Lee writes:]
> >I am using the term "elevation" to represent vertical
> >angle from the horizon, where the local true horizon
> >is 0 degrees and the zenith (overhead) is 90 deg.
> As I mentioned, that is an unusual meaning. The
> conventional coordinates are altitude and azimuth.
This is indeed confusing. Some blame goes to the aerospace industry for
having taken it upon itself to reuse, in totally nonsensical ways, two
long-existing terms with well-established meanings, namely, altitude and
elevation. They should be thoroughly thrashed with a wet noodle. And
they should stop. How many people will have to die before they decide to
rectify their mistakes?
Properly, elevation is the distance above mean sea level (MSL) in meter.
(SI has dropped plurals, presumably for the convenience of non-native
speakers). Altitude is the complement of the zenith distance. Zenith
distance is the angle from the zenith. Conventionally, altitude is
measured in degrees (of arc), with the zenith at 90 and the geometrical
horizon at 0.
Vertical angle is something different. See my earlier post (from late
summer?) in the SeeSat-L archive.
Whatever altitude for the true horizon you determine, I would expect it to
be quite low, because I recall seeing a very decent green flash at Sun
rise, looking East from a ninth or tenth floor hotel window somewhere near
Stapleton Airport in Denver, Colorado, USA.
BTW, by definition, Sun rise (at sea level) occurs when the geocentric
zenith distance of (the center of) the Sun is 90 degrees 50 minutes.
Jay Respler wrote:
> All sats have NAMES in addition to #.
Yes, but these names can be very troublesome indeed. This is one reason
I always try to give all 3; catalog number, COSPAR id and vulgar name.
'Course I still haven't seen agreement about what format should be used
for the COSPAR id, even among those who like it.
> QUICKSAT
...
> QUICKSAT
...
> QUICKSAT
Atta'boy, Jay. It certainly seems worth the trouble to me. It also seems
that an ephemeris server to run it, together with a team of computors and
updaters of orbits, would make a great deal of sense. It is my perception
that much of the remaining "activation energy barrier" from Molczan's Law
lies in the difficulty of elset maintenance. The team might consist of
Ted Molczan, Mike McCants, TS Kelso, Bj"orn Gimle, Alan Pickup, Pierre
Nierinck, Rainer Kracht, Ron Dantowitz, (myself? in this crowd, despite
my extensive experience with Mir and shuttles, I'm definitely a junior
member) and other trusted computors (my apologies to anyone I've
forgotten).
If it is thought necessary for performance reasons to limit access, my
guess is that a public server allowing one day's worth of successful
requests per day per location, each request being for a single evening or
morning (or a 6-hour night, near the poles) would be quite serviceable.
People with special requirements could be authorized to make particularly
deep or lengthy searches. Those who are regular (or irregular, for that
matter) contributors to SeeSat-L could probably be authorized without
further qualification. If such a server existed, perhaps NASA and the RSA
could be persuaded to update it directly, particularly for shuttle
maneuvers and Mir reboosts. Wouldn't that be a treat! (Mike, do you
recognize here any threads from my previous email?)
Indeed, the server might be intelligent enough to recognize regular
requests and pre-compute them in its spare time, thus avoiding CPU
bottlenecks.
Ted Molczan writes:
> >of course, there's always
> >3) There's nothing to explain. The pattern didn't exist before about ten
> > years ago, not that many satellites have flown subsequently,
> > and the pre-solstice "pattern" is most likely a fluke of small-
> > sample statistics.
> I like that explanation the best.
Normally I am on the side of those whose rant and rave about small sample
size. But I am surprised (what is wrong with the stupid Americans
spelling this word with "ised"?) to read of your opinion, because the
pattern has been established so long.
I've read here recently about some nice observations. Congratulations.
Cheers.
Walter Nissen dk058@cleveland.freenet.edu
resident, Pale Blue Dot
---
Carl Sagan, 1934-1996, explained in a most compelling way to millions of
students why what they are learning in science classes is so surpassingly
important; important to students, to people, to our species.