5. The catalogue - Discussion of the data

5.1. The data

At the end of this paper, the data are given. For each observed event, Tables 3 give the determined date of the minimum of light and the magnitude drop. In these tables, we also give the corresponding calculated data using 3 ephemerides and 2 algorithms. Both ephemerides are issued from Lieske's work (1977): G-5 ephemerides are fitted on photographic observations made from 1891 to 1978 (Arlot 1982), E-3 ephemerides are fitted on observations of several kind mostly eclipses by Jupiter made from 1652 to 1983 (Lieske 1987) and E-2 ephemerides are fitted on recent photographic data and old eclipses (Lieske 1980). Two algorithms were used (denoted (1) and (2) in the catalogue). The first one supposes that both involved satellites are uniform disks and the second one takes into account the phase defect and uses the Hapke's law (Hapke 1986) of diffusion of light to describe the apparent disks of the satellites whose surfaces are always supposed to have an uniform albedo (Thuillot & Morando 1990; Descamps 1992). For each event and each site of observation, we give also:

1. the () of the observation;
2. the type of telescope used in column "Inst." (denoted "T" for a reflector and "L" for a refractor);
3. the aperture of the telescope in centimeters;
4. the type of receptor in column "Recept." (cf. Sect. 3);
5. the elevation of Jupiter and the Sun upon the horizon in the two next columms;
6. the apparent distance from the involved satellites to the center of Jupiter in jovian radii;
7. the observational conditions in column "Obs. cond.": [1] means very good conditions; [2] means acceptable and [3] very difficult conditions;
8. the eventual filter used during the observations in column "Filter";
9. the time-sampling of the light curve in seconds of time.
10. the size of the diaphragm when used;
11. the satellites in the diaphragm, i.e. the satellites, the global magnitude drop of which was observed.

Figure 3 gives all the lightcurves in the same chronological order as the Tables. The light curves reported from VBO (Kavalur) correspond to the light variation of the occulted or eclipsed satellite. The contribution of the occulting or eclipsing satellite were determined before and after the observation and were substracted from the total flux so that, for this site, the observed lightflux drops are not comparable with the others.

These data and light-curves are available for anyone who is interested through the electronic network on the WEB server (http://www.bdl.fr) and on the ftp anonymous server (ftp://ftp.bdl.fr, directory: /pub/NSDC/jupiter/pheno_mut/1991) of Bureau des longitudes.

 

given in Description the tables Single channel receptors

PM1 photom. EMI9502B (Bucarest, Beograd)

PM2 photomultiplier EMI9789QA (Belogradchik, Catania)

PM3 photom. Quantacon RCA 31036 Ga-As (ESO)

PM4 photom. Hamamatsu EMI6256SA S-11 (ESO)

PM5 PIN photodiode OPTEC SSP13 (Essen, Holtsville, GEA)

PM6 photom Hamamatsu R647 1P21 (Kakuda)

PM7B photom. RTC 2020 (Nice)

PM7R photom. Hamamatsu 6375 (Nice)

PM8 photom. EMI9558QB (Cluj-Napoca)

PM9 photom. RCA 4840 (Paris)

PM10 photom. EMI9789QB (Reggio Calabria)

PM11 photom. RCA 6199 (Rio de Janeiro)

PM12 photom. attached to Siding Spring tel.

PM13 photom. EMI9862QB (Timisoara)

PM14 DOAA photod. SSP (Zoetermeer)

PM15 photom. Hamamatsu 943-02 (Brasopolis)

PM16 photom. RCA C31034A (Mauna Kea)

PM17 photom. HPO(1P21) or OPTEC SSP5

PMB photom. TELOC II channel B (Calern)

PMV photom. TELOC II channel V (Calern)

PMR photom. TELOC II channel R (Calern)

PMK photom. EMI9658R (Kavalur)

S20 photom. EMI9658B S20 cathode (Kavalur)

S20R photom. EMI9658R S20R cathode (Kavalur)

S11 photom. with S11 cathode (Jungfrau)

PMIR photometer IRPHOT2 1.5 micrometers (OHP)

PM unidentified photomultiplier Two-dimensional receptors

CCD1 c. CCD camera with TH7852 target (Bordeaux)

CCD2 c. CCD camera Astriane (Pic du Midi)

CCD3 c. CCD camera with TC-211 chip (Bowie) IR-A

CCDV1 video mode unc. CCD SBIG

CCDV2 video mode unc. CCD Sony ICX021

CCDV3 video mode unc. CCD Imaintel

CCDV4 video mode unc. CCD with intensifier

CCDV5 video mode unc. CCD Panasonic 0.5 lux

CCDV6 video mode unc. CCD Philips 56470 NXA 1011/01

CCDVX video mode unc. CCD MXRII HCS Vision Techn.

N video mode unc. SIT Vidicon (Nocticon) Other types of receptors

V visual observation using Argelander method

PH photographic observation

 

5.2. Discussion

In this paper, we do not intend to make a complete analysis of the data. These data may be analyzed for astrometric purpose as well as for planetologic interpretation. However, it is interesting to compare the different predictions and also the difference between the midevent defined as the closest approach of the two satellites -case (1)- and as the minimum of light -case (2)-. Note that some of the data presented in this catalogue for comparison with the other results have been analyzed yet by Mallama (1992), Froeschlé et al. (1992), Le Campion et al. (1992), Descamps et al. (1992) and Souchay et al. (1992).

Because of the very different time constants used for each observation, the quality of each lightcurve may be judged either with the value of the errors on the determinated parameters (time of the minimum of light and magnitude drop) or with the appearance of the lightcurve itself. The error bars are calculated as follows: - the error on the magnitude drop comes from the standard deviation from the fit to the model light curve (this explains that the error will decrease when the number of points decreases by averaging several successive points); - the error on the date of the minimum is deduced from the error on the magnitude drop combined with the speed of the decrease of the magnitude during the event (this explains that this error depends on the number of points, on the integrating time and on the depth of the light curve). Because of that, the errors bars may be compared only between events made with the same time constants and, preferably, with the same equipment. One will notice some bad determinations of the magnitude drops: this comes from the difficult conditions in which the corresponding observations have been made (small elevation above the horizon, twilight, vicinity of Jupiter or bad meteorological conditions). So, the two informations, time of the minimum of light and value of the magnitude drop do not have to be mixed in a single positional (). In a first step, the observed time of the minimum of light is more confident for theoretical studies.

We note that a good model is needed to fit the observed light curves, in order to determine accurate times of minimum light and magnitude drop. Such a model can also allow to observe beginning and ending times of the event to be determined. The predictions based on such a model can be directly compared to observations. Finally, a reduction that accurately models the albedo features and limb darkening of the satellites will give the best relative positions of the two satellites at the time of the event (Descamps et al. 1992; Mallama 1991; Mallama 1992).