Accession Number : ADA304787

Title :   Helicopter-Mounted Laser Beam Characterization Test 2.

Descriptive Note : Final rept.,

Corporate Author : ARMY RESEARCH LAB WHITE SANDS MISSILE RANGE NM

Personal Author(s) : Palacios, Fernando R. ; Watkins, Wendell R. ; Crow, Samuel B. ; Billingsley, Daniel R.

PDF Url : ADA304787

Report Date : JAN 1996

Pagination or Media Count : 56

Abstract : The effectiveness of a laser designator is dependent on the intensity and size of the beam placed on a target. This report describes a laser beam spread and wander test conducted at Holloman Air Force Base on August 18, 1994, by the Army Research Laboratory. To assess the performance of a helicopter-mounted laser, the beam was characterized by viewing and analyzing the diffuse reflections from a target board. The results are compared to a similar test conducted on June 7, 1994. Measurements were made to determine the impact of the platform (on which the laser designator was mounted) and environment on beam characteristics for a helicopter-mounted mid-infrared (IR) laser. A large reflective surface (2.44 by 2.44 m) target board was used to determine beam size and intensity. The board contained a hot blackbody (IR) source to guide the laser tracking system in directing the laser beam to its surface. The 30-Hz-frame- rate, mid-IR imager was used to characterize the diffuse reflections of the 1 OO-kHz, repetively pulsed, mid-IR laser beam. Data were recorded for the helicopter engine on/off, different hovering altitudes, and different ranges from the helicopter to the stationary reflective target board. When the helicopter was on the ground at 500-m range and with strong optical turbulence, there was some decrease in the beam spreading when the helicopter rotor was on, compared to when the rotor was off. When the helicopter was hovering and rotated so the exhaust and laser were pointed toward the target board, there was a bimodal beam geometry formed that changed shape with range and, presumably, is related to the air compression changes caused by the rotor downwash and refractive index changes in the exhaust plume.

Descriptors :   *LASER TARGET DESIGNATORS, ARMY RESEARCH, REFRACTIVE INDEX, TURBULENCE, HELICOPTER ROTORS, REFLECTION, LASER BEAMS, INFRARED LASERS, INFRARED IMAGES, HOT SPOTS, DIFFUSION, INFRARED RADIATION, BLACKBODY RADIATION, ALTITUDE, DUAL MODE, EXHAUST PLUMES, DOWNWASH, HOVERING, INTERMEDIATE INFRARED RADIATION, HELICOPTER ENGINES, LASER TRACKING.

Subject Categories : Helicopters
      Lasers and Masers
      Infrared Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE