Re: List of Bright Satellites - Why is it prepared Manually?

Sat, 14 Dec 1996 09:41:33 -0700

Hi Dave (et al.),

I am a developer of a satellite viewing program (SatSpy for Windows) and
I thought I might try to address some of your issues.  I am a software
with over 16 years of experience, 10 of which were spent developing tracking 
software for NORAD, the US Space Command and other agencies.  I can only
speak for
myself and my software, so let me describe how I approached some of these
design issues:

First: Visual Magnitudes

SatSpy uses two different approaches to providing visual magnitudes.  In
2.0, I added a estimated visual magnitude mode, using data and formula
by Ted Molczan, that computes the magnitude at each point in a pass.  If
you want
to know which bright passes will occur in a particular evening, you can
open a 
window showing all of the passes sorted by estimated visual magnitude.  SatSpy
retains a second mode (from v1.0) that uses empirical magnitudes that I
from various sources, including my own observations.  This mode is
primarily useful
for estimating the relative brightness of different sats rather than

Second: The question "what can I see tonight?"

SatSpy lets you answer this question in a couple ways.  First, you can open a
Viewing Opportunities window.  This shows all passes over a period from 10
to 10 days.  The passes are shown as time lines (similar to a Gantt chart)
so that
you see at a glance what is going over and when.  Furthermore, the passes are 
color coded (green=best, yellow=marginal, red=poor).  You have the option
to define
what is a good pass and what is not (defaults are provided).  You also can
filter out
daytime and shadow passes.  You can set your time period to start at
specific local
times, such as the start of nautical or astronomical twilight.  Once you
have opened
the window, you can click on any of the passes to bring up supplementary
including Skytraces (projection of the pass against your local sky),
groundtraces and
3D Orbit Views.

The other approach is the Multiple Skytrace window which shows all passes for
a period of time up to 45 minutes.  This time the pass are shown as
against your local sky.  The passes are color coded, to show when portions
of the 
pass are sunlit and in the earth's shadow.  All of the same filters apply
to this window as well.

Once you have figured out the answer to what you can see tonight, you can open
a Single Skytrace window for each pass.  From here, you can attach time and 
magnitude labels for any step in the ephemeris.  This will show you exactly
the satellite passes near a particular sky feature and the estimated
at each step.

Third: Automation

All of the filters,etc. described above can be predefined and stored in your
initialization file.  When you want to know what is up tonight, you perform
following steps: 1) load your elsets, 2) specify the time period of interest,
3) open a Viewing Opportunities window, 4) pick the passes you want, 5) print
skytraces for those passes and 6) go watch the satellites.

In closing,  I apologize to any who may be offended by my long description
of a particular program.  However, if you would like to try it for yourself,
you can download a copy from  
BTW, I also post an elset file ( that contains over 1100 of my
favorite elsets.  This is updated weekly from elsets found at the JPL site
(Ted Molczan's file) and the Celestial Archives (, visual.tle and


At 11:47 AM 12/14/96 +0000, you wrote:
>>I am wondering why, with all of the satellite-prediction software
>>we have today, it is still necessary to ask this question, especially
>>since magnitude estimates can be found in Ted Molczan's elements
>>file. Why doesn't one of these programs simply run through the
>>elements list, calculate a predicted magnitude, and if it shows
>>up brighter than a predicted magnitude, print it out? So far as
>>I know, only QUICKSAT does something close to this. However, it
>>uses its own file of predicted magnitudes which are actually
>>'greatest ever' brightness rather than 'expected' brightness,
>>which results in a lot of predicted passes that are not seen.
>>Is there some other software package that gives this information?
>No! You are not alone. I have been lurking on this list for a couple of
>months, a satellite newbie trying to get into this exciting field. Until
>your post I assumed I was being stupid. For the novice at any rate, it seems
>frustratingly difficult to get simple information.
>What a newbie wants to know (and perhaps an oldbie also?) is "what can I see
>tonight?" not "hmmm...I have a sudden inexplicable urge to look at Cosmos
>1741 r - I wonder when it's visible?".
>For me, the satellite software approach cannot take off (sorry) until all
>current element sets are easily and transparently available to the user from
>a definitive source. So the approach I use is to print the marvellous page at
>(I live in London). But even here the information is ordered *by satellite*
>not by event, so I have to scan through the list looking for the right
>day/time, checking to see if the elevation is great enough, and if the pass
>is sunlit (it took me a while to get to grips with that stuff, but I can
>read it now). Then I have a satellite number, but, frustratingly, not a
>satellite name (I find it hard to "bond" with the small integers).
>May I briefly describe my fantasy satellite software? I cannot see why *any*
>user input is required after starting the application. Assuming that I have
>already configured my location and UTC-offset, and that the application
>comes with nice default "sight quality" cutoff values (eg for
>magnitude/elevation/visibility-time), then I want to immediately see a
>summary list of forthcoming time-ordered events, each event having a single
>local date/time and a satellite name. If I press one button I want expanded
>information (the more detailed location/visibility data).
>The list that I see can be "filtered" according to various criteria. For
>example, one set of buttons will let me increment/decrement each of the
>"sight quality" values, in each case refreshing the list in order to reflect
>the new criteria. Other filters could be established by the user (eg
>favourite satellites, flashing satellites). I'm sure the knowledgeable ones
>here can identify the important filters.
>(I feel sure that if "Bill" were into satellites it would be done this way
>My comments are intended to be constructive criticisms, I hope no-one is
>offended by my presumption. Although I am a satellite neophyte, I earn my
>living as a software developer. The currently available software is
>fantastic in terms of speed and accuracy, but does make certain assumptions
>about the level of technical skill and motivation of its users.
>glad to have "broken cover"
>Dave Ziemann