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We report on 18 months of multiwavelength observations of the blazar 3C 454.3(Crazy Diamond) carried out in July 2007-January 2009. We show the results ofthe AGILE campaigns which took place on May-June 2008, July-August 2008, andOctober 2008-January 2009. During the May 2008-January 2009 period, the sourceaverage flux was highly variable, from an average gamma-ray flux F(E>100MeV) >200E-8 ph/cm2/s in May-June 2008, to F(E>100MeV)~80E-8 ph/cm2/s in October2008-January 2009. The average gamma-ray spectrum between 100 MeV and 1 GeV canbe fit by a simple power law (Gamma_GRID ~ 2.0 to 2.2). Only 3-sigma upperlimits can be derived in the 20-60 keV energy band with Super-AGILE. DuringJuly-August 2007 and May-June 2008, RXTE measured a flux of F(3-20 keV)=8.4E-11 erg/cm2/s, and F(3-20 keV)=4.5E-11 erg/cm2/s, respectively and aconstant photon index Gamma_PCA=1.65. Swift/XRT observations were carried outduring all AGILE campaigns, obtaining a F(2-10 keV)=(0.9-7.5)E-11 erg/cm2/s anda photon index Gamma_XRT=1.33-2.04. BAT measured an average flux of ~5 mCrab.GASP-WEBT monitored 3C 454.3 during the whole 2007-2008 period from the radioto the optical. A correlation analysis between the optical and the gamma-rayfluxes shows a time lag of tau=-0.4 days. An analysis of 15 GHz and 43 GHz VLBIcore radio flux observations shows an increasing trend of the core radio flux,anti- correlated with the higher frequency data. The modeling SEDs, and thebehavior of the long-term light curves in different energy bands, allow us tocompare the jet properties during different emission states, and to study thegeometrical properties of the jet on a time-span longer than one year.

Multiwavelength observations of 3C 454.3. III. Eighteen months of AGILE monitoring of the "Crazy Diamond"