Leo Barhorst (leobarhorst@pi.net)
Tue, 21 Jan 1997 21:26:08 +0100

PPAS database - clean up and watching

1. Introduction

The database of Photometric Periods of Artificial Satellites (PPAS) has been
collected over the years by the Belgian Working Group of Satellites. It contains
the flashobservations of Jean Meeus, Bertus Kroon, Horst Kohnke, Bram
Dorreman, Bart de Pontieu, Leo Barhorst, Kurt Jonckheere, Tristan Cools,
Pierre Neirinck, Russell Eberst, Mike McCants and many others who despite
extreme cold and other harsh circumstances persevered and produced such a
vast amount of data.

The first PPAS was issued in 1990 and in early 1996 PPAS6 was distributed to
the observers through the internet (SeeSat-L) and on the flashdisk. Monthly
supplements assure each observer of an up-to-date archive of flashobservations.

Up to PPAS6-06 the total amount nears the  40.000 observations. A lot of these
observations are from satellites that have already decayed, so no further data of
these satellites will be added to the PPAS (unless ofcourse some old archive
shows up). Of the satellites still in orbit there are a lot that were not observed 
for some time,  from one to more than 20 years.

2. PPAS clean-up

For some time I have been thinking about a PPAS clean-up and started  this in
december 1996.

The goals of this clean-up are:
a) Split the PPAS data base in two parts; one containing all the observations of
the satellites still in orbit, the PPASyy.obs files, where yy is the launchyear of
the satellite; the other part containing all observations of decayed satellites, the
DECAYyy.obs files;
b) Working through the first part and checking which satellites, not observed
for long, should be observed as soon as possible;
c) Doing a) and b) I've and shall come to (minor) faults in the PPAS files and
correct them.

Achieving the goals:
a) Using my satellite data base and a text editor I've started splitting the PPAS
b) With Satflash I've printed as far as possible the Flash Period Graphs of all
satellites in the PPAS files and started with printing the 5 most recent
observations (if available) of the satellites still in orbit;
c) Collecting the (minor) faults, such as wrong Cospar ID (satellite and/or
fragment doesn't exist in the Noradcataloge), wrong date (mostly the year),  ect.
I'll report to Kurt Jonckheere for correcting them in the upcoming PPAS7

3. The PPAS ORBIT program

I'm willing to coordinate and maintain the PPAS  Observe on a Regular Basis In
Time program 
and alert the observers on SeeSat-L which satellites should be observed as soon
as possible and depending on the results with what frequency. Once ORBIT is
running I hope alerting will not be needed anymore, as all observers pick now
and then some 'old' satellite, as Willy Verhaegen and I are already doing.

ORBIT updates will be posted to SeeSat-L regulary as well as the resulting
observations by either Kurt in his PPAS updates or by me.
Send your ORBIT observations with all your other observations to the
collecting adress:

4. The first results

Printing all the Flash Period Graphs resulted in more than 500 graphs, ranging
from 3 to 500+ observations. The PPAS file splitting allows me to concentrate
on the satellites still in orbit. For the years 1959 (no observations of satellites
launched in 1957 and 1958 are reported to PPAS) to 1967 a total of 119
satellites remain. The satellites in the observation program of PPAS and
observed regulary will not be discussed here anyfurther, although they are
included in the table, of which a small part is printed below.

Cospar ID	numb	Last obs	Period	Days since
		obs	date			last obs
59-  1 B 	3	5-08-91		22,52	1997
59-  9 A 	1	22-11-75	0,5	7732
60-  2 B 	2	2-01-94		S	1116
60-  7 A 	3	23-01-95	var	730
60-  7 C 	10	26-01-89	S	2918
60-  9 B 	18	13-10-75	0,85	7772
60- 14 A 	2	22-07-93	I	1280
61- 15 A 	3	24-03-89	I	2861
61- 18 A 	475	24-02-96	148	333
61- 28 A 	136	30-04-96	45,9	267

In the last column are listed the days since the last observation untill the actual
systemdate of the computer; they can be updated automatically every time the
file is opened and the actual daynumber has changed.

As is clear in the above table 59-  9 A and 60- 9 B should be observed as soon
as possible. Are they still flashing? Also 59-  1 B needs to be looked at. The two
PPAS program objects stand out clearly with their low value in the last column
and high number of observations.

5. Conclusion

I hope all observers will contribute to ORBIT in order to keep an eye on the
'old' flashers. It will be not the first time that a satellite, with a long period or
even steady, suddenly accelerates and becomes a nice flasher once again.

Any comments may be posted on SeeSat-L or directly to my own e-mail adress.

Greetings and clear skies

Leo Barhorst		Alkmaar			The Netherlands
52.65 North		4.767 East		1 m ASL
Member of Seesat-L
Every day I wonder about the things I see in the (night)sky