SATPC0037013 Tab 04 4 SOW .pdf

Statement of Work (SOW)

RCS Measurements of Calibration Objects

19 September 2024

This SOW covers the requirements for an RCS measurement facility to provide RCS measurements of calibration objects supplied by NASA.

1.0 Background

Radar cross section (RCS) measurements of calibration objects, i.e., objects with well-known radar backscatter characteristics, e.g., spheres and dipoles; or objects with well-characterized shapes and constituent materials are being selected for RCS measurements to facilitate future computational model validation, evaluation of test facility capabilities, and comparison with similar measurements conducted in an optical measurement facility. Measurements of simple calibration objects were completed in August 2023. This work expands on that effort by introducing calibration objects with more complex materials and/or shapes.

1.1 Test Articles and Setup

Calibration objects will be provided by NASA as described in Table 1. Objects described in the table are representative of what will be provided to the test facility prior to commencement of RCS measurement activities; however, the exact configuration and quantity may change due to the time it takes to conduct measurements and/or the number of test days available.

Table 1. Representative calibration objects to be tested in an RCS facility.

Test Shape Material Dimensions

2-1 Tapped Sphere Al 2.699 cm diameter

2-2 Tapped Sphere Al 2.699 cm diameter

2-3 Tapped Sphere Al 2.699 cm diameter + paint

2-4 Tapped Cylinder Al

28.575 mm (1.125 ") diameter x

85.725 mm (3.375") length

2-5 Plate CFRP 3 cm x 3 cm x 3.175 mm

2-6 Rod SS 1.27 cm (0.5”) dia., <1 cm length

2-7 Plate PCB (FR4) 3 cm x 3 cm x 1.57 mm

2-8 Plate with holes CFRP

Choose size from Round 1 targets

2-9 FR4 ‘Sandwich’ PCB (FR4) 3 cm x 3 cm x 3.14 mm

2-10A Bent CFRP Plate CFRP

3.175 mm (0.125”) thickness, 16” legs will be cut down

2-10B Bent CFRP Plate CFRP Same as 2-10A 2nd orientation

2-11 Hollow Pipe SS 1.27 cm (0.5”) outer diameter

2-12A Half Pipe SS 1.27 cm (0.25”) outer radius

2-122 Half Pipe SS Same as 2-12A 2nd orientation

2-13 Bent CU Rod Cu 3.175 mm diameter

2-14 Solar panel fragment Solar panel Irregular ~2 cmx2cm chip

A test fixture will be provided by NASA to integrate the test articles, described in Table 1, with the test facility’s test stand – which may be a foam tower or some type of positioner with azimuth rotation capability. NASA and the test facility shall agree on the final test article interface or test fixture used. An example test fixture is shown in Figure 1. The test fixture is anticipated to rest on a foam tower or test positioner provided by the facility, which can be rotated in azimuth. The azimuth rotation method is provided by the test facility and will support RCS distribution measurements.

Figure 1. Example test fixture, constructed from low-loss foam, to interface a calibration object being tested with the facility test stand.

1.2 RCS Measurement Tasks

RCS measurement tasks are outlined below. Initial measurements will need to be made for the test article holders described above to allow for subtracting out the response of the holder itself from the measurements of the calibration objects integrated with their holders. Note that for at least some of the RCS measurements conducted, NASA intends to send representatives to review the measurement process at the test facility, and to provide guidance and clarification as the test article expert while measurements are conducted to ensure that the result of testing is valuable for future use of the data.

1. For each calibration object, the RCS test facility shall conduct RCS measurements at azimuth and elevation angles agreed upon by NASA.

2. For each calibration object, the RCS test facility shall conduct RCS measurements from

2 – 18 GHz in 0.1 GHz steps, or at frequency steps agreed upon by NASA.

3. For each calibration object, the RCS test facility shall collect and provide full polarization matrix data, i.e., HH, HV, VH, and VV polarization at each azimuth and elevation angle pair, where H = horizontal, V = vertical. The first letter in the sequence designates the transmitter polarization, and the second letter designates the receiver polarization.

4. For each calibration object, the RCS test facility shall convert the full polarization matrix data into right-hand and left-hand circularly polarized backscattered field components and provide this data to NASA. This data will include the azimuth and elevation angles, as well as the frequency the data was collected at.

1.3 RCS Measurement Deliverables

The RCS test facility shall provide the following information to NASA:

1. The full polarization matrix data (HH, HV, VH, and VV) at each azimuth and elevation angle pair and each frequency the data was collected at.

2. The full polarization matrix data converted into right-hand and left-hand circularly polarized backscattered field components, including the azimuth and elevation angles, as well as the frequency the data was collected at.

3. Any drawings, illustrations, photographs, and/or video of the test setups and RCS measurements as they are being conducted.

4. A test report, which may be in the form of a document or presentation, summarizing the results of the RCS measurements conducted.

It is desired that example measurements, as in item 1, be provided to NASA after each of the first several tests to assess if the measurements are understandable and suitable for meeting the test objectives, and to inform any changes in procedure that may be required.

1.4 Additional Facility Requirements and Other Considerations

1. The RCS test facility vendor shall provide evidence that they are able to conduct RCS measurements of objects that are of similar size, material, and construction as those listed in Table 1 in the frequency band of interest.

2. Test facility experience with measuring RCS for objects like those listed in Table 1 and demonstrated performance with past projects for NASA or other customers will be considered in determining a suitable test facility vendor.

3. Lead times and flexibility in scheduling will be considered in determining a suitable test facility vendor.