The Department of the Air Force, Air Force Materiel Command, Air Force Life Cycle Management Center, Bombers Directorate, B-2 System Program Office has a requirement for the Low Observable Signature & Supportability Modifications (LOSSM) program’s analysis, integration, test, database generation and sustainment.

• Low observable (LO) maintenance relies on periodic inspections to identify Radar Cross Section (RCS) signature defects. These inspections can be visual observations (Tier 0), probe point inspection measurements (Tier 1), or higher fidelity radar signature measurements. The currently fielded Tier I system measures predefined measurement points on the aircraft using a Radio Frequency (RF) probe suite consisting of three different types of probes: (1) a probe that measures highly conductive materials such as paint, transparent materials and tapes using an open ended resonant waveguide cavity, (2) a probe that measures MAGRAM absorbers using an open ended waveguide reflectometer, (3) a probe that measures R-card using a microstrip sensor. All 3 categories of probes are designed to measure materials as installed on the aircraft that are integrated into material stacks. The waveguide-based probes utilize several sizes of waveguide to measure over the operational frequency bands of interest.
• The probes are connected to a vector network analyzer (VNA) via radio frequency (RF) cables. The VNA includes operator input keys and a display. The VNA is connected to a laptop computer for primary system interface, display, and data storage. The data is transportable to other diagnostic systems. Routine operation of the current probe point inspection system includes a brief warm-up of the system, VNA calibration, probe calibration and probe measurement of a predefined area. Types of measurement data that are generated and collected include reflection coefficients and sheet impedances. These responses are compared against a known measurement value.

• The B-2 SPO foresees several candidates as improvement and replacement options: (1) system(s) containing an integrated VNA eliminating the existing stand-alone VNA and RF cable which induces measurement errors from cable flexure and damage, (2) new primary interface and software, (3) replacement system(s) that are easier to use and more accurate. (4) The system must be Class I, Division 2 of the National Electric Code (NEC), Article 500.5(B), (5) The system must execute Radio Frequency point inspections, i.e. not zonal, not visual and not whole body. Visual cueing of the probe for alignment to predefined measurement points or defects is acceptable and is currently the method employed, (6) system(s) must be able to be transported, calibrated, and operated by a single user.
• The Contractor shall perform training systems tasks and meet training support objectives. The training system tasks include, but are not limited to, analysis, evaluation of system designs, development, production, installation, integration, test, database generation, and sustainment. Tasks also include documentation reviews, participation in design and management reviews, cost/schedule status tracking, technical data library management, and configuration and data management activities.
• Specifically, responses should address the following:
  • Experience integrating, development and/or ability to integrate miniaturized VNAs, and eliminate larger VNAs and RF cables.
  • Recommended system technologies/architectures/physicals (e.g. probe)
  • Methods to consolidate equipment
  • Designs and certification approaches to meet the requirements of Class I, Division 2 of the National Electric Code (NEC), Article 500.5(B)
  • Open systems architecture implementation
  • Approaches that minimize diminishing manufacturing source risks
  • Approaches that could accelerate measurements
  • VNA and probe calibration methodology
  • RF measurement error and uncertainty for each proposed probe type.
  • Security, sanitization and protection of classified data during proposed system operation, and storage.
  • The point inspection system should be able to be operated, carried, and manipulated by 1 maintenance technician for long periods of time in various positions such measuring regions on the underside or top of the aircraft.