     Photometric Periods of Artificial Satellites
     --------------------------------------------

1. Introduction

This database of Photometric Periods of Artificial Satellites (PPAS)
has been collected by the Belgian Working Group of Satellites (BWGS). 
It can be used for research on flash periods of artificial satellites. 
So far research on this subject has been hampered by the lack of obser-
vational data. We hope this database can leviate that problem.

The idea to create this database came from Christian Steyaert who dis-
covered the old archive of Jean Meeus (with observations from 1962 until
1978) in 1988. While working on the informatisation of the (new) obser-
vations of the BWGS (which restarted its activities in 1987), the idea 
grew to collect all old observations as well. Apart from Jean Meeus'
archive another major source was found in Bertus Kroon's archive. The 
observations of the Dutch group that formed around him limited the gap 
between Jean Meeus' archive (until 1978) and the current activities of
the BWGS (from 1987 onwards new observations guarantee a follow-up).

2. Versions

PPAS 1 was published in October 1990. 
PPAS 2 appeared at the end of 1991. Added were new observations ob-
tained between August 1990 and September 91, and some older observations 
(obtained from the archives of our active observers).
PPAS 3 appeared at the end of 1992. The archive of Pierre Neirinck and 
Daniel Karcher was added, as were all new observations between September 
91 and August 92.
PPAS 4 was published early 1994. New observations between August 1992 and 
November 1993 were included. Some small errors were also corrected.
PPAS 5 appeared in January 1995. Part of the archive of the late
Horst Koehnke was added, as were all observations obtained between
December 1993 and December 1994.
PPAS 6 was published in April 1996. It contains more of the archive of
Horst Koehnke, as well as new observations obtained between December 1994 
and March 1996. The remarks-file PPAS6.REM was cleaned up and the indexing
of the remarks was improved.
PPAS 7 appeared in May 1997.  It contains another part of the archive
of Horst Koehnke, as well as new observations obtained between April 1996
and May 1997.  Thanks to the effort of mainly Leo Barhorst a number of
faulty entries in our archive were corrected.
PPAS 8 appeared in January 1999.  It contained a number of observations
of Mike McCants' archive, as well as new observations obtained between
May 1997 and December 1998.


3. Collaborators

Our thanks go to the following people:

 - Bart De Pontieu, Bram Dorreman, Kurt Jonckheere, Kurt Osaer, Christian
   Steyaert and Patrick Wils who entered all PPAS 1 observations.
 - Jean Meeus, Bertus Kroon, Pierre Neirinck and Horst Koehnke for their 
   archives.
 - Dirk Carlens, Tristan Cools,  Bart De Pontieu, Johannes Fritzer, Kurt 
   Jonckheere and Jan Vansteelandt for entering the archives of Pierre 
   Neirinck and Horst Koehnke.
 - Kurt Jonckheere for collecting our monthly observations until July 1992.
 - Bart De Pontieu for collecting our monthly observations between July 1992 
   and May 1993.
 - Tristan Cools for collecting our monthly observations from May 1993 until 
   April 1996.
 - Kurt Jonckheere and Leo Barhorst for collecting our monthly observations
   from April 1996 until August 1996.
 - Kurt Jonckheere for collecting our monthly observations from August 1996 until 
   December 1998.
 - all observers for sending in their monthly observations since 1991.

Further acknowledgement goes to the following persons :

PPAS 1 : Bram Dorreman for first editing, uniformisation and synchronisation 
	 between the different sources of PPAS 1. 
PPAS 2, 3, 4 : Bart De Pontieu and Kurt Jonckheere for uniformisation and
	       final editing of these PPAS versions.
PPAS 5 : Tristan Cools for uniformisation and final editing of PPAS 5.
PPAS 6 : Tristan Cools for uniformisation and final editing of PPAS 6.
PPAS 7 : Kurt Jonckheere for uniformisation and final editing of PPAS 7.
PPAS 8 : Kurt Jonckheere for uniformisation and final editing of PPAS 8.

Finally we would like to thank all observers, who despite such hazards as
cold, frustration, fights with the family and other harsh circumstances 
persevered and produced such a vast amount of scientific data.


4. Technical details

The PPAS consists of 41 Text or ASCII-files (one for each launch year) which
contain the observations of the satellites launched in that year. All PPAS-
files have the extension '.OBS'. E.g. The file 'PPAS91.OBS' contains all
observations of satellites which were launched in 1991.

It should be noted that the names of all satellites launched before 1963 have
been COSPAR-ized. Official notation uses Greek letters for them. We have chosen
to translate all Greek names to the current COSPAR system (to avoid trouble
with the Greek characters). e.g. 61- alpha kappa 4 becomes 61- 34 D.  
USSPACECOM have also adopted this system in 1993.

The file 'PPAS8.REM' contains remarks that were too long to be fitted into the
80 column PPAS-format (see below). The remarks are numbered per satellite.
The numbers in the remarks column of the PPAS-format (e.g. '1)') refer to
the PPAS7.REM file.

5. Special format

Every line (each line is ended by an 'end-of-line' character) contains one
observation. In order to make processing easy, we have used a standard format.
In this format each line is divided in columns and every column always con-
tains the same data. Normally each line contains 80 columns (or characters),
but in order to save space on the disk, every line is ended if the remaining
characters are blank.
This is the format which has been used:

Column       Data
01-08        Cospar-identification of the satellite in the format
	     yy-nnncc. yy is the year of launch, nnn is the number
	     of the launch (only contains significant numbers and
	     is right justified), cc is the piece of the launch (contains
	     non-numeric characters). e.g. '86- 39 B' was launched in
	     1986 as the 39 th launch and it was a rocket (B). Normally
	     an 'A' represents a payload, while everything starting with
	     'C','D',... is usually debris. An important exception are the
	     Russian C-1 rockets who transport 8 payloads in one into space.
	     They always have 'J' as extension.

10-17        Date of observation in the format yy-mm-dd. Here all figures
	     are given (even non-significant numbers). e.g. '76-03-01' is
	     March 1 in 1976.

19-28        Time of the observation in the format hh:mm:ss.t . All times
	     are given in Universal Time (UT). Hours (hh) are measured from 0
	     to 23 h. Minutes from 0 to 59 minutes, while seconds can be
	     given up to one tenth of a second. Depending on the accuracy
	     with which the time was measured, the time can be incomplete.
	     A lot of observations merely contain the hour. These are mostly
	     observations of the Meeus archive. Attention should be paid to
	     observations of which the time is given in this format :
	     hh:mm.t. This gives hours, minutes and tenths of a minute. Some
	     observers use it to show their accuracy is lower than 1 second.
	     This field is blank if no time has been given by the observer.

30-32        An abbreviation of the name of the observer. A list of all abbre-
	     viations and the observing place of each observer is given below.
	     The abbreviation used, may differ from the initials to avoid
	     duplicate identifications.

34-38        Total time in seconds and tenths of a second which passed during
	     the measurement of the flash period, in the format sss.t . Only
	     recent measurements contain this information. It can be used to
	     estimate the effect of a wrong count of periods and to check the
	     given period (see below). It is blank if not applicable.

40-42        Accuracy in seconds and tenths of a second on the total time if
	     the total time is given. If the total time field is blank, the
	     accuracy relates to the period. Some inputs contain '.nn'. This
	     means the accuracy (probably on the period) is 0.nn seconds.

44-46        The number of periods counted. The total time divided by the
	     number of periods gives the flash period.

48-53        Flash period in seconds and tenths, hundredths (or even thou-
	     sandths) of a second in the format ss.tht . The 'point' is
	     always found at position 50 unless the period is larger than
	     99.999 seconds. The number of figures given is related to the
	     estimated accuracy. Usually larger periods have smaller accu-
	     racy (i.e. they are less accurate!). This field is blank if no
	     period has been measured or if (more likely) the object did
	     not show any variation in brightness. In this last case, the
	     object is 'STEADY'.

55-80        Remarks on the flash-pattern or on other aspects of the passage.
	     A list of abbreviations which are commonly used is given below.
	     Normally all remarks are in lowercase, except for 'S' (steady,
	     which always comes on position 55 if applicable) and some other.
	     All remarks on one observation are divided by commas. Some
	     remarks contain numbers in the format 'n)', e.g. '1)'. This is a
	     reference to the PPAS.REM-file, which has also been put on the
	     disk.
	     This file contains remarks which were too long to be put in
	     the usual place. Using the name of the satellite and the number
	     of the reference it is possible to link both files in mind.


6. Abbreviations in the PPAS-remarks.

The various remarks are separated by a comma and a space. E.g. S, mag +4. The
format for describing the satellites' magnitude is: mag maximum_magnitude->
minimum_magnitude.
The '+' is omitted for the minimum_magnitude. E.g. mag +4->8  .
When the minimum is invisible, this is indicated with 'inv', e.g.
mag +5->inv. Some observers only mention the maximum_magnitude,
e.g. mag +5.
The following abbreviations are used in the PPAS-remarks-column.


    ?       the photometric period is uncertain, or the remark which
	    accompanies this question mark is uncertain.

    a       the photometric period is an approximation.

    amp     amplitude

    b       the observation has been made with binoculars.  This applies
	    to most measurements, but is sometimes mentioned explicitly.

    dec     decreasing in brightness. (sometimes mentioned with sm)

    df      two flashes in one period.

    dif     different (maxima)

    dm      double maxima: two close maxima in one period.

    dp      double period: the period measured, has been taken between
	    three (instead of two) similar points in the light curve.

    dtm     the period was difficult to measure.

    fm      flat maxima: the brightness remained fairly steady during a
	    relatively long time.  Because of this the exact moment of
	    maximum is difficult to define.

    hp      half period: the period measured was half of the real period.

    I, irr  irregular brightness pattern, irregularly varying.

    inc     increasing.

    lp      long period.

    min     the period has been measured on the minima in brightness.

    N?      the counted number of maxima is uncertain.

    occ     occasionally.

    ph      photographic observation.

    pm      primary maxima.

    qm      quadruple maxima: four maxima in one period.

    R       regularly varying

    S       the brightness did not (or only very slightly) change,
	    except for the variation caused by the change of phase-angle.

    sa      small amplitude : there is a small difference in brightness between
	    a maximum and a minimum.

    sec     secondary.

    sf      short flashes, possibly used as maxima.

    sm      a relative (secondary) maximum occured between two absolute
	    maxima.

    ssm     some secondary maxima were visible.

    tm      triple maxima: three maxima in one period.

    u       an observation made with the unaided eye.

    var     varying (usually used in the phrase 'slowly var').

    V       varying

    vm      the observed maxima varied in brightness during the observation.

It is possible that even other abbreviations were used. If you would notice
an abbreviation which is not in this list, please report this.

To describe the peculiarities of the flash-pattern (without drawing figures),
the following symbols are put into groups depending on the pattern observed:

    A       smooth primary (or absolute) maximum.

    a       like 'A' but secundary or relative.

    F       sharp (like a flash) primary (or absolute) maximum.

    f       like 'F' but secundary or relative.

    M       flat primary (or absolute) maximum.

    m       like 'M' but secundary or relative.

    _ or -  indicates a minimum or the absence of a (expected) maximum.

    '       the apostrophe usually indicates the maximum on which was counted.
	    Sometimes used with _ or - to indicate that the minima were
	    counted.

    ,       the comma indicates the location of the minimum which was used to
	    count the periods.

Some examples are given below:

     A'A'     a regularly varying object with primary maxima only.

     A'aA'    a regularly varying object with secundary maxima. Primary maxima
	      were used to count.

     A'FA_A'  this pattern occurs very frequently in case of Soviet A2-
	      rockets. A maximum is followed by a flash (comparable in
	      brightness), by another maximum, after which the next flash is
	      absent. After this, the pattern is repeated.

     A'fA_A'  the same as the previous one, but the flash is less bright.

     a'Fa_a'  in this case the flash is definetely brighter than the smooth
	      maxima.

     M,M      a pattern with two flat maxima divided by a sharply defined
	      minimum (which was used to count the periods).

     F'F'     a pattern which has flashes only.



7. Observers of the PPAS

AB     A.C. Beresford            Adelaide                  Australia
AF     Alain Figer               Martigues, Paris          France
ANO    Antero Olkkonen           Ristiina                  Finland
AP     Alphonse Pouplier         Wepion                    Belgium
AR     Alberto Rango             Livorno                   Italy
AS     Alexander Seidel          Lemgo                     FRG
                                 Stade/Elbe                FRG, from 1983 on
BB     Bjorn Bonny               Eernegem                  Belgium
BD     Bram Dorreman             Achel                     Belgium
BDP    Bart De Pontieu           Oostende                  Belgium
BG     Bill Gates                Albuquerque, New Mexico   USA
BJG    Bjoern Gimle              Junibacken                Sweden
BK     Bertus Kroon              Apeldoorn                 The Netherlands
BP     Bengt-John Piolon         Oostende                  Belgium
BPW    Bruce P. Watson           Denver                    USA
BV     Boris Vrancken            Oostende                  Belgium
BY     Brad Young                Tulsa, OK                 USA
CE     Christopher Engelhardt    Fulda                     FRG
CK     ?
CS     Christian Steyaert        Geel                      Belgium
CT     Cal Tech                  California                USA
CW     Chris Wyatt               Bendigo, Victoria         Australia
DA     A. d'Allessandro          Genua                     Italy
DAP    David Alan Pickup         Edinburgh                 Scotland
DB     David M. Brierley         Manchester                Great-Britain
DC     Dirk Carlens              St.Lambrechts-Herk        Belgium
DG     Doyle J. Groves           Noblesville, Indiana      USA
DH     David Hopkins                                       Great-Britain
DIB    Dietmar Buettner          Chemnitz                  Germany
DJL    D.J. Lazlo                Denver, Colorado          USA
DK     Daniel Karcher            Wittenheim                France
DL     Dirk Laurent              Mechelen                  Belgium
DM     Harry De Meyer            Sint-Kruis, Brugge        Belgium
DMB    David M. Brierley         Colorado Springs          USA
DSB    Douglas Biggerstaff       Toronto                   Canada
DW     D. West                   Austin, Texas             USA
DWB    David W. Bishop           Utica, New York           USA
EC     Ed Cannon                 Austin, Texas             USA
EL     Ed Light                  Lakewood, NJ              USA
EN     Elisabeth Nuyts           Kessel-Lo                 Belgium
ER     Eero Rantalaiho           Varkkala                  Finland
EV     Eric Vondra               Wampum, PA                USA
FD     Frank Dempsey             Ajax, Ontario             Canada
FF     Franco Foresta            Palermo, Sicily           Italy
FR     Frank Reed                Scottsdale, Arizona       USA
FV     Fritz Verhelst            Ekeren, Antwerpen         Belgium
FW     Frank Weissferdt          Selters                   FRG
GAR    Greg Retzlaff             Saskatchewan              Canada
GH     Gary Holahan              Silver Spring, Maryland   USA
GL     Ulrich Gentzel-Lingner    Heidelberg                FRG
GM     Gunter Monz               Peterberg                 Germany
GR     Greg Roberts              Kaapstad                  South-Africa
HA     ?
HB     Hermann Boehnhardt        Rodental-Moenchreden      FRG
HD     ?
HK     Horst Koehnke             Stade-Elbe                FRG
HS     Hermann Schnitzler        Grevenbroick              FRG
HVB    Hendrik Vandenbruane      Beernem                   Belgium
IL     Inge Leyssens             Edegem                    Belgium
IP     ?
IPO    Ian Porter                                          Australia
JA     Jan Aelbrecht                                       Belgium
JC     Johan Claes               Oostende                  Belgium
JDW    Jean De Weerdt            Gistel                    Belgium
JDG    Don Gardner
JEV    Jim Varney                Sacramento, California    USA
JG     Jason Gibson              Melbourne                 Australia
JH     Johan Hoste               Oostende                  Belgium
JHR    Jay H. Respler            Freehold, New Jersey      USA
JL     Jean Lecacheux            Meudon                    France
JM     Jean Meeus                Kessel-Lo (till 67-06-30) Belgium
                                 Korbeek-Lo                Belgium
                                 Erps-Kwerps (fr 16-07-68) Belgium
JN     Jim Nix                   Memphis, TN               USA
JO     J. Oudman                 Groningen                 The Netherlands
JOP    Joel Piraux               Marseille                 France
JP     John Prentice             Albuquerque, New Mexico   USA
JPH    Jason Hatton              Strasbourg                France
JR     J. Ruland                 Hasselt                   Belgium
JR     Juergen Renn              Moers                     FRG
JS     Jan Strobbe               Eernegem                  Belgium
JSC    Jim Scotti                Tucson, AZ                USA
JV     Jaap Veltekamp            Vries                     The Netherlands
                                 Groningen                 The Netherlands
JVB    Jan Vandenbruane          Beernem                   Belgium
JVS    Jan Vansteelandt          Leuven                    Belgium
JVW    Jeroen Van Wassenhove     Nazareth                  Belgium
JW     Joel Weisberg             Albuquerque, New Mexico   USA
KAH    Kai Hamalainen            Lappeenranta              Finland
KB     Ken Boedt                 Oostende                  Belgium
KD     Kurt Dequick              Bredene                   Belgium
KDL    Kris Delcourte                                      Belgium
KH     Kevin Hestir              Albuquerque, New Mexico   USA
KJ     Kurt Jonckheere           Oostende                  Belgium
KO     Kurt Osaer                Bredene                   Belgium
KVG    Karin Van Genegen         Mortsel                   Belgium
LA     Georges Lauwers           Zemst                     Belgium
LB     Leo Barhorst              Ede + Alkmaar             The Netherlands
LG     Lloyd R. Gibson           Thallon, Queensland       Australia
LL     L. Langeville             Brussels                  Belgium
LP     Lieven Van Parijs         Meulebeke                 Belgium
LR     Leo Rajala                Jamsa                     Finland
LS     Lutz Schindler            Braunschweig              Germany
LW     Leo Wikholm               Helsinki                  Finland
MA     D.C. Mason                Tremadoc,Caernarven,Wales Great-Britain
MAD    Madison                                             USA?
MAG    Mauritz Geyser                                      South-Africa
MD     Alistair Macdonald        Toronsville               Australia
MF     Matthew Francey           Mississauga, Ontario      Canada
MG     ?
MJ     Michel Jacquesson         Sevigny-Waleppe           France
MM     Mike McCants              Austin, Texas             USA
MO     Marc Moors                Bonheiden                 Belgium
MPM    ?
MR     Mike Rosseel                                        Belgium
MS     Markku Siljama            Mantyharju                Finland
MVP    Michel Van de Putte       Ronse                     Belgium
MW     ?
MZ     Grupo Espacial            Mendoza                   Argentina
NB     N.J. Budd                                           UK
NC     Neil Clifford             Oxford                    UK
PA     Peter Aneca               Bredene                   Belgium
PC     Patrick Carpreau          Mechelen                  Belgium
PDV    Patrick Devreese          Moen                      Belgium
PEW    Peter Wakelin             Ascot, Berkshire          UK
PIA    Pieter Audenaert          Gent                      Belgium
PK     Petteri Kankaro           Merimasku                 Finland
PM     Paul Maley                Houston, Texas            USA
PN     Pierre Neirinck           Malo-Les-Bains            France
PP     Pieter Passchijn          Eernegem                  Belgium
PR     Paul Roggemans            Mechelen                  Belgium
PS     Patrick Schmeer           Saarbruecken-Bischmisheim Germany
PW     Patrick Wils              Niel                      Belgium
                                 Boortmeerbeek             Belgium
RD     Rudy Dequick              Bredene                   Belgium
RE     Russell Eberst            Edinburgh, Scotland       Great-Britain
RGL    Ron Lee                   Falcon                    USA
RIK    Richard Keen              Coal Creek                USA
RK     Rainer Kracht             Elmshorn                  Germany
RM     Rob Matson                Belmont Shore, CA         USA
RMC    Ralph McConahy            Barstow, CA               USA
RO     Jean-Pierre Rohart        Wormhout                  France
RS     Robert Sheaffer           San Jose, CA              USA
RW     Ron Welch                 Watson                    Australia
SA     Sacramento                California                USA
SL     Stefan Lobet              Kontich                   Belgium
ST     San Antonio               California                USA
SW     Sue Worden                                          USA
TC     Tristan Cools             Brugge                    Belgium
TD     Tommy Deslijpere          Oostende                  Belgium
TH     Terre Haute                                         France
TID    Tim Daniels               Edegem                    Belgium
TK     Takeshi Kawabata          Yokohoma                  Japan
TM     ?
TR     Tuomo Roine               Helsinki                  Finland
TT     Tuomas Torronen           Espoo                     Finland
VAG    Vince Gardiner                                      Australia
VB     Isi Van den Broeck        Londerzeel                Belgium
                                 Duffel                    Belgium
VC     Paul Van Cauteren         Aartselaar                Belgium
VG     Vincent Gathot            Eernegem                  Belgium
VH     Luc Vanhoeck              Puurs                     Belgium
VI     Van Iseghem               Sint-Kruis, Brugge        Belgium
VL     Frans Van Loo             Itegem                    Belgium
VM     Veikko Makela             Helsinki                  Finland
VN     Van Nuys                                            Belgium
WD     Werner Depoorter          Halle-Zoersel             Belgium
WH     Wim Holwerda              Loon-op-Zand              The Netherlands
WJW    William J. Welker         Pittsburgh                USA
WN     Walter Nissen             Silver Spring             USA
WPK    Willie Koorts             Wellington                South Africa
WV     Willy Verhaegen           Wetteren                  Belgium
YY     Yoshiro Yamada            Yokohama                  Japan

(As of 1999,)
In total 166 observers produced 48648 observations. If possible the location of 
the observations has been given. Some observers have moved or made observations 
on a vacation trip. There is one double identification i.e. the initials JR are 
the same for Juergen Renn and J. Rulandt (both made one observation)/
There are a few unidentified observers, whose names have been lost. None have
made more than a couple of observations. 
Half of the observers have made less than 50 observations. Some of those are not
very experienced, which might influence the quality of the observations.
More than 50 observers are active at this moment. An asterisk '*' is given
next to the name of the active observers. All satellite observers are warmly 
encouraged to join our group.


6. Use of PPAS

The PPAS is free of charge. It is updated regularly with new observations. The 
updates are available from the same archive as where you find this text.
For more information contact the address below.
If you happen to notice errors, please report them. Also, all users are
invited to send their own observations (in the PPAS-format) to us.
All information on future versions of PPAS will appear on SeeSat-L and on
the www-pages of the Visual Satellite Observers Home Page. 

It may be interesting to note that the BWGS has developed a software package 
(SatFlash) which facilitates analysis of the PPAS data.

The PPAS-data may be used for scientific analysis, provided the source 
is mentioned.

You can find more information about the Belgian Working Group Satellites
on the Visual Satellite Observers Home Page:

http://www.satobs.org/tumble/tumbleintro.html
http://www.satobs.org/tumble/flashpm.html
http://www.satobs.org/tumble/rotandfp.html
http://www.satobs.org/tumble/rottheory.html
http://www.satobs.org/tumble/expresfpm.html

  Bram Dorreman
  Kurt Jonckheere
