We summarize the results of observations made between 10 Jun. - 18 Dec. 1988 with the International Ultraviolet Explorer (IUS) of comet P/Tempel-2 during its 1988 appearance. The derived water production rate and relative gas/dust ratio are compared with those of P/Halley, observed with IUE in 1985-86, and other potential Comet Rendezvous/Asteroid Flyby (CRAF) target comets, P/Kopff and P/Tempel-1, both observed with IUE in 1983

Feldman, Paul D.

Festou, Michel C.

English

NASA Technical Reports Server

' r,J --.67Asteroids,Comets,Meteors1991,pp. 171-174
LunarandPlanetaryInstitute,Houston,1992 / _ _f-'_
f--
N93-19153
IUE Observations of Periodic Comets TempeI-2,
171
Kopff and Tempel-1
P. D. Feldman
Department of Physics and Astronomy
The Johns Hopkins University
Baltimore, MD 21218, USA
M. C. Festou
Observatoire Midi-Pyr_n_es
31400 Toulouse, France
ABSTRACT
We summarize the resultsof observationsmade between I0 June and 18 December 1988 with
the InternationalUltravioletExplorerofcomet P/Tempel-2 duringits1988 apparition.The derived
water production rate and relativegas/dust ratioare compared with those of P/Halley,observed
with IUE in 1985-86, and other potentialCRAF targetcomets, P/Kopff and P/Tempel-1, both
observed with IUEin 1983.
I. INTRODUCTION
Periodiccomet Tempel-2 (1988 XIV) isthe currentprimary targetcomet for the Comet Ren-
dezvous/AsteroidFlyby (CRAF) mission.It was alsothe targetcomet in 1987 so thatextensive
observationswere planned foritsapparitiontoprovideinformationabout the gas and dust environ-
ment to be expected forthe spacecraftand the scientificnstruments.Although the CRAF project
scheduleled to a subsequent change in targetto periodiccomet Kopff (1983 XIII),observationsof
Tempel-2 by the International Ultraviolet Explorer (IU_ satellite were carried out as planned over
the period 10 July to 18 December 1988 and produced ultraviolet spectra on ten separate dates
during this period. The observation parameters are listed in Table 1, together with the measured
brightness (in a nominal 10."3 x 15"1 aperture) of the OH(0,0) and CS(0,0) bands at 3085 A and
2575 A, respectively. Also given is the continuum flux in a 100 A wide band centered at 2950 A,
reduced to the parameter Alp defined by A'Hearn et al. (1984). Here, A is the mean grain albedo,
fis the filling factor of the grains in the aperture and p is the radius of the aperture.
II. COMET P/TEMPEL-2
The derivedwater production rateshave already been presented by Roettger et al.(1990).
They are summarized in Table 1 and shown in Figure 1 as a functionofheliocentricdistance,r.
To facilitatea comparison with previouslypublishedproduction ratesderivedfrom IUE data, the
ORIGdNAL PAOE !$
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https://ntrs.nasa.gov/search.jsp?R=19930009964 2020-03-17T07:32:09+00:00Z
172 Asteroids, Comets, Meteors 1991
Table 1: Observational data
Comet/Date r(AU) A(AU) Boff(R) Bcs(R) Afp(cm) Qx2o(s -1) Qcs(s -1)
P/Tempel-2
1988 June 10 1.72 0.79 45 - < 40 1.1×102r -
1988 July 28 1.48 0.80 640 20 60 1.2)<1028 5.6)<1024
1988 August 20 1.42 0.86 1500 60 110 2.4×1025 1.7×1025
1988 September 6 1.39 0.92 2130 - 120 3.5)< 1028 -
1988 September 14 1.38 0.94 2100 65 100 3.6)<1028 1.8)<1025
1988 September 29 1.39 1.02 2510 70 130 3.8)<1028 2.2)<1025
1988 October 4 1.40 1.04 2570 75 110 3.6)<102a 2.4)<1025
1988 October 28 1.45 1.21 2620 60 120 3.2)<1028 2.4)<1025
1988 November 15 1.52 1.36 1700 - 150 2.4)<1028 -
1988 December 18 1.69 1.74 510 - 140 12)< 102a -
P/Kopff
1983 July 18 1.59 0.81 1960 50 430 5.1x102a 3.5x102s
P/Tempel-1
1983 July 18 1.50 1.00 450 20 160 1.0)<102a 5.4x1024
model used in the derivation assumed a parent molecule velocity of 1.0 km s-1 independent of r.
The CS production rates are also given in Table 1, assuming a short-lived parent (presumably CS2),
and the ratio Qcs/Q_t2o derived from the data is in the range of 5 - 8 )< 10 -4, typical of all comets
observed by IUE at this range of heliocentric distances. The H20 production rate follows the same
pre-/post-perihelion asymmetry as exhibited by the visual light curve, as has been demonstrated
by ttoettger et al. (1990).
, , , , i , , _ '/'':'r' I ' '1029
5
- ! I F l i i
__ @
× +
x
[] +
x P/Tempel-2 pre-perihelion
+ P/Tempel-2 post-perihelion
_-" 1028 --
ID
) 5-
<:y
1027 -
x
5 , I,,,
1.3 15 1.8 i17
r (AU)
o P/Kopff
o P/Tempel- 1
,,,, I,,,,I,,,,I,,,
1.4
1
1.8 _
Figure 1: Water production rate as a function of heliocentric distance.
Figure 2 shows the values of Q1_2o/Afp as a function of heliocentric distance. This quantity
is a measure of the gas-to-dust ratio in the coma, although it is model dependent in that the
assumptions of a constant ratio of dust velocity to gas velocity and a constant dust size distribution
Asteroids, Comets, Meteors 1991 173
100
50 -
o
X
10 --
I I
x + P/Tempel-2
o P/Kopff
O P/Tempel- 1 -
××
+
o
D
_ , , I I I
0.7 1.0 2.0 30
r (AU)
Figure 2: The ratio of water production rate to Alp as a function of heliocentric distance.
as a function of heliocentric distance are required for this quantity to be proportional to Qga,/Qa,,t.
A comparison with other comets is given in Figures 3 and 4. The first of these is an updated
version of a similar figure from Feldman and A'Hearn (1985), and with the caveat noted above,
indicates that at larger heliocentric distances, the ultraviolet continuum appears to dominate the
gas emission. Even so, there is a clear indication of varying gas/dust ratios in this sample of comets.
Figure 4 shows QH2o/AfP for comets P/Halley (1986 III), Wilson (1987 VII) and Bradfield (1987
XXIX), three "dusty" comets observed over a wide range of heliocentric distances by IUE. These
data indicate a variation in gas/dust with heliocentric distance, as is also indicated for P/Tempel-2,
although over a much more limited range of r, in Figure 2. For P/Tempel-2, all of the continuum
measurements were made at phase angles between 40 and 46 °, so a change in observational geometry
cannot be responsible for the range of QH2o/AfP values.
o
X
o"
I00
50
I0
B: Brmdfleld (1979 X)
D: P/D Arrest ""2
a E: P/£ncke ."
a G: P/Giaeobini-Zlnner-
T K: P/Kopff 1
M: Meier (lSSO XI[)
G A P: Panther (1981 ll)
S: P/Stephan-Oterma
M T: P/Turtle
a b: P/Brorsen-Metcall
D K a: Austin (1989ct)
---- B
5 -
t , , I I I
o.7 1.o 2.0 3.0
r (AU)
Figure 3: Same as Figure 2 for several comets observed by IUE.
OF POOR QUAtffY
174 Asteroids, Comets, Meteors 1991
III. OTHER CANDIDATE COMETS
Figures 1 and 2 and Table 1 also include similar data for comets P/Kopff (1983 XlII) and
P/Tempel-1 (1983 XI), two other potential CRAF mission targets. These data were obtained
on a single date, 18 July 1983, so that no information is available about the evolution of these
comets with time from IUE. Nevertheless, it is possible to infer that near their perihelia P/Kopff
is somewhat more active and "dustier" than P/Tempel-2, while P/Tempel-1 is less active and also
fairly "dusty".
!
O
X
o
,.r
o'
' ° I
100 --
50 -
10 - +
+x +
5 - ×x + +
×
x x ° o
I i i l
0.7 1.0
+ xlHalley (1986 hl)
Q Wilson (1987 VII) -
o Bradfield (1987 XXIX)
+
O
+
+
rl
x
ox
+x+
x
x
i
2.0
r (AU)
,D
X X
×
o
I
3.0
Figure 4: Same as Figure 2 for three "dusty" comets.
ACKNOWLEDGEMENTS - _::_: =::7
This work was supported by NASA grant NSG-5393.
.... REFERENCES
A'Hearn M. F., Schleicher D. G., Feldman P. D., Millis R. L., and Thompson D. T. (1984) Comet
Bowell 1980b. Astron. J., 89,579-591.
Feldman P. D. and A'Hearn M. F. (1985) Ultraviolet albedo of cometary grains. In Ices in the Solar
System (J. Klinger, D. Behest, A. Dollfus, and R. Smoluchowski, eds.), pp. 453-461. Kluwer
Acad. Publ:; Dordrecht.
Roettger E. E., Feidman P. D., A'Hearn M. F., and Festou M. C. (1990) Comparison of water
production rates from UV spectroscopy and visual magnitudes for some recent comets. Icarus,


IUE observations of periodic comets Tempel-2, Kopff, and Tempel-1

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