Type: Periodic Perihelion date: 27 December 2023 Perihelion distance (q): 1.8 Aphelion distance (Q) : 5.8 Period (years): 7.3 Eccentricity (e): 0.53 Inclination (i): 44.0 JPL orbit diagram COBS lightcurve 1783 W1 = 2003 A1 = 2009 R2. LINEAR discovered a 19th mag comet on 5 January 2003. Although parabolic orbital elements were published, Brian Marsden noted on MPEC 2003-A56 [8 January 2003] that the object was probably of short period, and that its orbit was rather similar to that of comet D/1783 W1 (Pigott). Further observations, published on MPEC 2003- A86 confirmed the short period nature of the orbit, with perihelion at 1.91 AU, a high inclination of 46 degrees and a period of 7.1 years. This was LINEAR's 100th comet. Orbital calculations by Maik Meyer tended to confirm the identity of the object with D/1783 W1. Nakano has computed a linked orbit: If the comet has made 33 revolutions from 1783 to 2003, this provides a good linkage between D/1783 W1 and P/2003 A1. Because the period of the comet is not certain, the number of revolutions of the comet could be between 37 and 29. Furthermore, in the case of 33 revolutions, the comet made several close approaches to Jupiter. The closest approach to the earth during this time was at the appearance of 1783. An apparently asteroidal LINEAR object discovered on 5 January 2003 with m2 18.4, posted on the NEO Confirmation Page, was found to be diffuse by CCD observers elsewhere, including at Haleakala (1.2-m reflector, with K. Lawrence reporting the object as slightly diffuse on NEAT images taken on 7 January and again somewhat diffuse on 8 January), at Klet (where M. Tichy found a coma diameter of 8" on images taken on 8 January with the 1.06-m KLENOT reflector), and at Ondrejov (where P. Pravec found a faint, small coma that was "marginally apparent", on images taken close to the moon on 8 January with the 0.65-m f/3.6 reflector). The object is likely of short period, with the angular orbital elements quite similar to those of D/1783 W1. Rich Kowalski discovered a very diffuse comet during the Catalina Sky Survey with the 0.68m Schmidt on 10 September 2009. Dimitry Chestnov linked the object to comet 2003 A1, although the linked orbit had considerably different orbital elements (notably T and q) to those predicted for 2003 A1. Brian Marsden notes on IAUC 9072: "it is meaningless to indicate a Delta(T) value because the prediction is strongly influenced by a very close approach to Jupiter (nominally 0.0605 AU on 10 September 2006)." He then computed a linked orbit that satisfactorily included observations of comet Pigott, seen in 1783. Observations (VEMag = visual equivalent magnitude) Date 10x10 mag Error VEmag Coma ' 05-Oct-16 16.10 0.01 13.7 0.4 28-Oct-16 16.20 0.03 13.8 0.5 23-Nov-16 15.82 0.02 13.6 0.4 19-Dec-16 17.33 0.03 14.5 0.5 27-Dec-16 17.81 0.04 15.5 0.4 04-Jan-17 16.91 0.03 15.3 0.4 15-Feb-17 19.16 0.13 17.3 0.2