urn:nasa:pds:clementine1_bistatic:document:offsqnt 1.0 1.21.0.0 Product_Document Cwik, T.; Jamnejad, V. 1997 This document describes small polarization dependent pointing offsets observed when using DSN beam-waveguide (BWG) antennas. No BWG antennas were used during the Clementine bistatic radar experiment, but some of the same concepts may be used to explain apparent offsets between RCP and LCP pointing at DSS 14. This file is accompanied by a detached PDS label (OFFSQNT.LBL) which completely describes the document. The document is in Adobe Portable Document Format. 2024-04-25 1.0 Product migrated to PDS4 from PDS3. 1997-02-15T00:00:00Z 1998-01-15T21:21:23Z Deep Space Program Science Experiment Mission urn:nasa:pds:context:investigation:mission.deep_space_program_science_experiment document_to_investigation Clementine 1 Clementine 1 Host urn:nasa:pds:context:instrument_host:spacecraft.clem1 is_instrument_host Radio Science Subsystem Instrument urn:nasa:pds:context:instrument:clem1.rss is_instrument Moon Satellite urn:nasa:pds:context:target:satellite.earth.moon document_to_target Cwik, T.; Jamnejad, V. 1997-02-15 Document describes small polarization-dependent pointing offsets for NASA Deep Space Network (DSN) beam waveguide antennas. Document was sent by Mike Wert of the DSN to Sal Abbate, accompanied by the note below. Abbate then forwarded both to Stanford where analysis was being carried out. The 'article' mentioned in the first paragraph is this document. No ASCII text version was available at the time the archive was constructed. No beam waveguide antennas were used for the Clementine bistatic radar experiment; but 'squint' concepts may still be useful for understanding differences in system noise when the 70-m antennas were pointing at the lunar limb. Sal, As you requested to assist in your understanding of differences in the microwave noise observed between the two circular polarizations at S-band at DSS14 during DSPSE bi-static lunar radar, I have researched the literature and found the attached article which explains the theory of offset-feed-induced-polarization-squint. The research attached was for the specific case of the new DSN beam-waveguide antennas, but the theory applies to the reflex optics used to illuminate the SPD cone S-band feed with the DSS14 cassegrain telescope. I have not 'run' the equations from the attached article for the specific optical constants for DSS14, but from field calibration results from Mr. D. Girdner, GDSCC, the following empirical results are available: 1. DSS14 S-band pointing is typically RCP-compensated 2. The LCP beam from DSS14 would be about 0.009 degrees positive in elevation from the RCP beam -- which is in agreement qualitatively with the attached paper (i.e. squint in the plane transverse to the plane containing the optic axis and the feed offset, and to the right for LCP radiation looking out along the beam) 3. The DSS14 main-lobe at S-band is about 0.1 deg wide (full-width at half-power) 4. The difference in received noise from the lunar disk from the two beams will depend on the aim point(s) used. If you can provide the aim point(s) used, a rough expected noise temperature set could be approximated. The observed squint at DSS14 could also be compared with the theoretical value to further qualify the noise expectation approximation. Regards, Mike Wert PDF Version English 1 offsqnt.pdf PDF