No abstract

The airborne ESA-APEX (Airborne Prism Experiment) hyperspectral mission simulator is described with its distinct specifications to provide high quality remote sensing data. The concept of an automatic calibration, performed in the Calibration Home Base (CHB) by using the Control Test Master (CTM), the In-Flight Calibration facility (IFC), quality flagging (QF) and specific processing in a dedicated Processing and Archiving Facility (PAF), and vicarious calibration experiments are presented. A preview on major applications and the corresponding development efforts to provide scientific data products up to level 2/3 to the user is presented for limnology, vegetation, aerosols, general classification routines and rapid mapping tasks. BRDF (Bidirectional Reflectance Distribution Function) issues are discussed and the spectral database SPECCHIO (Spectral Input/Output) introduced. The optical performance as well as the dedicated software utilities make APEX a state-of-the-art hyperspectral sensor, capable of (a) satisfying the needs of several research communities and (b) helping the understanding of the Earth's complex mechanisms.

Pentadiene was polymerized with the CoCl 2(P i PrPh2)2-MAO system, obtaining a crystalline polymer with a melting point of 168 °C. The polymer was characterized by IR, NMR ( 13 C and 1 H in solution and 13 C in the solid-state), DSC, GPC, and X-ray diffraction, and it was found to have a trans-1,2 syndiotactic structure. The fiber periodicity of 5.14 ( 0.03 Å indicates a trans-planar mainchain conformation similar to the one found in 1,2-syndiotactic polybutadiene. Molecular mechanics calculations using the MM2 force field show that, for trans-1,2 syndiotactic polypentadiene (t-12 sPPD), the all-trans main-chain conformation is more stable with respect to the (T 2G2) arrangement, consistent with structural data of most 1,2-syndiotactic polydienes but at variance with the cis isomer and with 1,2-poly(4-methyl-1,3-pentadiene). The crystalline structure of t-12 sPPD has been determined on the basis of a unit cell derived from fiber data and refined using the Rietveld method on unoriented patterns. Like both 1,2-syndiotactic polybutadiene and 3,4-syndiotactic polyisoprene, it adopts the high-symmetry orthorhombic space group Pbcm with the following refined lattice parameters: a ) 6.59(1), b ) 14.69(1), and c (chain axis) ) 5.11(3) Å. The two chains in the unit cell also present, besides crystallographic intramolecular glide planes, intramolecular 2-fold axes and planes of symmetry, both orthogonal to the glide plane. The main-chain conformation is slightly distorted from planarity, while the side chains adopt the same idealized skew arrangement found in other trans-1,2 syndiotactic polydienes. The refinement, giving the quality of the available data, is satisfactory. The thermal parameters, the relatively loose packing, and some features of the refined geometry points to disorder in the structure that we were unable to detail further using simple crystallographic models.

(Z)-1,3-pentadiene has been polymerized with the CpTiCl3−MAO system at −78 °C to a polymer consisting exclusively of cis-1,2 units and having a syndiotactic structure. The polymer has been characterized by NMR (13C and 1H in solution and 13C in the solid state), IR, DSC, GPC, X-ray, and molecular modeling techniques, comparing its conformational and structural properties with those of other 1,2-syndiotactic polymers. Diffraction and NMR data are consistent with the idea that a single crystalline polymorph prevails in the studied samples. The solid-state NMR results allow us to exclude the all-trans (T4) conformation for cis-1,2 syndiotactic polypentadiene and indicate a nonuniform helix of the T2G2 type as most plausible, although other possibilities such as the (T6G2T2G2) conformation cannot be completely ruled out. These conclusions follow from the fact that two conformationally distinct methylene C1 carbons are observed, which experience, respectively, zero and two γ-gauche interactions. Isolated chain molecular mechanics calculations too show that both (T2G2)2 and (T6G2T2G2) n conformations are of comparable stability, while the more extended all-trans (T4) arrangement has significantly higher internal energy, at variance with the situation found in most 1,2-syndiotactic polydienes. Simple qualitative considerations on the steric conflicts involving terminal cis methyls of the side chains of adjacent monomer units in the all-trans conformation rationalize this result.