# Test F3E - Limbs

Goal: One of the major conditioning terms that can be used for landmark position is limb data. While stereo is useful, the limbs provide a 90° orthogonal data set to constrain the landmark's position relative from center of figure (see Figure 8). However, limb images normally consist of approach images with low resolution. From theoretical calculations, we estimate the best we can get the accuracy to be is 1/2 to 1/4 of a pixel of a limb image. It would be useful to investigate inclusion of higher resolution images that do not contain the entire asteroid, but still get better limb constraints.

## Operator Information: Limbs Effects

Central vector. Running GEOMETRY, option 1 will adjust the spacecraft position/pointing. INIT_LITHOS has a weighting, LMKWTS, where the 2nd argument is the weighting used in the linear function used to solve relative to stereo (WB), limbs (WL), overlaps (WO), and a reference body (WR -- typically SHAPE00.TXT).

Spacecraft position/pointing. Running GEOMETRY, option 2 will adjust the spacecraft position/pointing. INIT_LITHOS has a weighting, PICWTS, where the 2nd argument is the weighting used in the linear function used to solve relative to stereo (WB), limbs (WL), nominal position (WS), nominal pointing (WC) and two images on either size (WT -- set with DYNAMICS).

Double feedback. GEOMETRY uses the landmark position to refine the spacecraft position. Additionally, it will update the landmark position based upon the spacecraft position. This can continue indefinitely.

We need to evaluate both the update to the central vector and the spacecraft position/pointing, thus each parameter of tests gets rerun to evaluate both the central vector and the spacecraft position/pointing.

## Test Set Up

Data: Approach and DS off nadir with new images

• 4 images with low stereo (e=10°) -- 5cm pixel size (DS images). Azimuth for spacecraft of 0°, 90°, 180°, 270°.
• 4 images with high stereo (e=45°) -- 5cm pixel size (DS images). Azimuth for spacecraft of 0°, 90°, 180°, 270°.
• 4 limb images with oblique angles (e > 80°) of each 1m, 50cm, 15cm, 5cm resolutions . Azimuth for spacecraft of 0°, 90°, 180°, 270°.

Start: 35cm Preliminary Survey Shape Model

Build: TAG #1 site (single location evaluation, (lat, Wlon) = (-8.027, 262.768))

### Sub-Test General Procedure

Start Up: Using PS shape, add in stereo images for the TAG site. Tile the full TAG site until we get a GSD of 5cm. Run GEOMETRY, option 2 to update the "stable" spacecraft positions/pointing.

Post Start Evaluation:

• Landmark Center Point Cloud Evaluation: Derive the point cloud of all the 5cm landmarks -- getting their central vector for every landmark. Then combine this point cloud into an obj and evaluating it to the truth model (shape 3.7) using CompareOBJ.
• Report out RMS of the point cloud.
• Measure the current displacement of the original position and pointing of the spacecraft and the updated position and pointing. Report the maximum deviation in distance (magnitude) and the deviation of all three camera angles.
• Do this for both the low stereo and high stereo images. Save these directories.
• Begin each Sub-Test

### Sub-Test Landmark Position

• Add in the [100cm, 50cm, 15cm, 5cm] limb images. Iterate five times to get the limbs connected and used fully.
• Running GEOMETRY, option 1 isn't needed because standard iteration does this option with a "v-1".

Evaluate:

• Derive the point cloud of all the 5cm landmarks -- getting their central vector for every landmark. Then combine this point cloud into an obj and evaluating it to the truth model (shape 3.7) using CompareOBJ.
• Report out RMS of the point cloud.

### Sub-Test Spacecraft

• Add in the [100cm, 50cm, 15cm, 5cm] limb images. Iterate five times to get the limbs connected and used fully.
• After running an iteration five times, run GEOMETRY, option 2, to update all the spacecraft positions/pointing.
• Evaluate the position and pointing of the spacecraft. We will look at the distance between the actual spacecraft position (from non-perturbed kernels) with the updated spacecraft object (SCOBJ) and camera (CX, CY, DZ) in SUMFILES.