26P/Grigg-Skjellerup

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**26P/Grigg-Skjellerup**
Discovery
Discovered by:	John Grigg and John Francis Skjellerup
Discovery date:	1902 and 1922
Alternate designations:	1808 C1; 1808 III; 1902 O1; 1902 II; 1902c; 1922 K1; 1922 I; 1922b; 1927 F1; 1927 V; 1927e; 1932 II; 1932d; 1937 III; 1937e; 1942 V; 1942d; 1947 II; 1947a; 1952 IV; 1952b; 1957 I; 1956i; 1961 IX; 1961g; 1967 I; 1966f; 1972 II; 1972b; 1977 VI; 1977b; 1982 IV; 1982a; 1987 X; 1986m; 1992 XVIII
Orbital characteristics ^A
Epoch:	April 10, 2007 (JD 2454200.5)
Aphelion distance:	4.9332 AU
Perihelion distance:	1.1168 AU
Semi-major axis:	3.0437 AU
Eccentricity:	0.6631
Orbital period:	5.31 a
Inclination:	22.36°
Last perihelion:	October 8, 2002 (unobserved)
Next perihelion (predicted):	March 23, 2008

Comet Grigg-Skjellerup (formally designated 26P/Grigg-Skjellerup) is a periodic comet.

Discovered in 1902 by John Grigg of New Zealand, and rediscovered in its next appearance in 1922 by John Francis Skjellerup, an Australian then living and working for about two decades in South Africa where he was a founder member of the Astronomical Society of Southern Africa.

In 1987, it was belatedly discovered by Ľubor Kresák that the comet had been observed in 1808 as well, by Jean-Louis Pons.

The comet has often suffered the gravitational influence of Jupiter, which has altered its orbit considerably. For instance, its perihelion distance has changed from 0.77 AU in 1725 to 0.89 AU in 1922 to 0.99 AU in 1977 and to 1.12 AU in 1999.

Having its recent perihelion so close to Earth's orbit made it an easy target to reach for the Giotto mission (spacecraft) in 1992, whose primary mission was to Comet Halley. Giotto had a closest approach to Grigg-Skjellerup of 200 km, much closer than its approach to Comet Halley, but did not get any pictures as its camera was destroyed during the Halley rendez-vous in 1986.

In 1972 the comet was discovered to able to produce a meteor shower, the Pi Puppids, and its current orbit makes them peak around April 23, for observers in the southern hemisphere, best seen when the comet is near perihelion.

The 2002 return (expected perihelion around October 8, 2002) was very unfavorable and no observations were reported.