# Newton-Raphson Test Plan

## Overview
Test cases for Newton-Raphson analytical propagation implementation, organized by implementation phase and test category.

## File Organization
Each test file requires a dedicated config file (1:1 mapping).
Total estimated test files: 13-14

## Current Progress (2026-01-31)

### Completed Tests (6/14 files fully passing)

#### 1. ✅ test_cartesian_to_elements_basic.cpp + .toml
- Status: PASSING (12/12 assertions) - FIXED
- Issue: NaN values in reconstructed radius/velocity
- Fix: Corrected true_anomaly calculation (line 122 in orbital_mechanics.cpp)
  - Changed: `r_dot_e / mu` → `r_dot_e / (r_mag * e_mag)`
  - Added: cos(ν) clamping to [-1, 1] before acos()
- Config: Moderate eccentricity (e=0.5), zero inclination
- Tests:
  - Round-trip conversion: orbital elements → state vectors → orbital elements
  - Position/velocity magnitude preservation
  - Semi-major axis, eccentricity accuracy

#### 2. ✅ test_newton_raphson_convergence.cpp (NO CONFIG)
- Status: PASSING (28/28 assertions) - FIXED
- Issue: Low eccentricity (e=0.001) test had incorrect expectations
- Fix: Changed test to verify Kepler's equation satisfaction instead of first-order approximation
  - Verify: |E - e·sin(E) - M| < 1.0e-10
  - Verify: |E - (M + e·sin(M))| < 0.01 (first-order approximation)
- Code changes: Refactored orbital_mechanics.cpp to separate elliptical/hyperbolic solvers
  - Added: `solve_kepler_elliptical()`, `solve_kepler_hyperbolic()`
  - Added: `eccentric_to_true_anomaly()`, `hyperbolic_to_true_anomaly()`
  - Added: `mean_anomaly_to_true_anomaly()` unified wrapper
- Config: Programmatically varied parameters
- Tests:
  - Very low eccentricity (e < 0.01): convergence rate verification
  - High eccentricity (0.9 < e < 0.99): iteration count limits
  - Mean anomaly near π: worst-case convergence
  - Large mean anomaly values (M > 1000): periodicity handling
  - Eccentricity at boundaries (e = 0.9999, 1.0001)

#### 3. ✅ test_analytical_propagation_apsides.cpp + .toml
- Status: PASSING (5/5 assertions) - FIXED
- Issue: Test measured velocity at same orbital anomaly (both at ν=0)
- Fix: Changed to measure velocity at ν=π/4, then compare to perigee velocity
  - Before: Both measurements at ν=0 (perigee)
  - After: Measure at ν=π/4, compare to ν=0
- Config: Elliptical orbit (e=0.6, a=2e7)
- Tests:
  - Propagation through perigee (velocity maximum)
  - Propagation through apogee (velocity minimum)
  - At exact orbital period: should return to initial state
  - True anomaly accuracy after full orbit
  - Vis-viva equation holds at multiple points

#### 4. ✅ test_analytical_propagation_timesteps.cpp + .toml
- Status: PASSING (7/7 assertions) - FIXED
- Issues: 3 test design bugs (tolerance, division by zero, 2π wrapping)
- Fixes:
  - Small timestep: Changed to check position error (difference from expected v·dt) instead of absolute position change
  - Division by zero: Added check for `expected_pos_error > 1e-6` before calculating relative error
  - 2π wrapping: Added circular angular error calculation using `fmin(raw_error, 2π - raw_error)`
- Config: Standard orbit (e=0.4, a=1.5e7)
- Tests:
  - Large timesteps: dt > 1 orbit period
  - Very small timesteps: dt < 1 second
  - Accuracy vs. timestep size relationship
  - Mean anomaly accumulation over long propagation

#### 3. ✅ test_extreme_eccentricity.cpp + .toml
- Status: PASSING (28/28 assertions) - FIXED
- Issue: Config validation failing for spacecraft too close to parent
- Fix:
  - Config: Fixed "Near_Parabolic" (e=0.99, a=7.0e8) and "Slightly_Hyperbolic" (e=1.05, a=-1.3e8)
  - Test: Added validation to skip testing ν outside valid range for e>1
    - For e>1: valid ν must satisfy |ν| < arccos(-1/e)
    - For e=1.05: max |ν| ≈ 2.83 rad (162°)
- Code changes: Added `validate_true_anomaly_ranges()` to config_validator.cpp
  - Checks hyperbolic orbits for true anomaly validity
  - Validates ν is within asymptote boundaries for e>1
- Config: Multiple spacecraft (e=0.99, e=0.95, e=1.05)
- Tests:
  - Numerical stability near e=1.0
  - Hyperbolic solver switching
  - Velocity magnitude accuracy
  - Period calculation (or lack thereof for e≥1)

#### 5. ✅ test_precision_boundaries.cpp + .toml
- Status: PASSING (15/15 assertions) - FIXED
- Issues: 2 bugs (1 test bug, 1 implementation bug)
- Fixes:
  - Test bug: Removed incorrect Z-coordinate check for polar orbit
    - Test expected Z = r·sin(i), which assumes motion along Z-axis
    - Actual position at perigee is on X-axis, so Z=0 is correct
  - Implementation bug: Fixed circular orbit velocity calculation in orbital_elements_to_cartesian()
    - Changed from constant velocity `vx=0, vy=v_mag`
    - To correct rotating velocity `vx=-v·sin(ν), vy=v·cos(ν)`
    - Angular momentum now properly conserved (error: 1.2e-14% instead of 41.4%)
- Code changes: Refactored orbital_elements_to_cartesian()
  - Added inline comments for each orbit type (circular/elliptical/parabolic/hyperbolic)
  - Consolidated calculation of semi-latus rectum p before velocity section
  - Reduced velocity calculation from 16 lines to 10 lines
  - Eliminated duplicate p = a·(1-e²) calculation
- Config: Multiple boundary cases (e=0, i=π/2, i=π)
- Tests:
  - Eccentricity at exactly 0
  - Inclination at 0°, 90°, 180°
  - Semi-major axis sign change
  - Angular momentum conservation

### Implementation Summary

**Code Changes:**
- Added to `src/orbital_mechanics.h`: Function declarations for
  - `cartesian_to_orbital_elements(Vec3, Vec3, double)`
  - `solve_kepler_equation(double, double)`
  - `get_initial_trial_value(double, double)`
  - `propagate_orbital_elements(const OrbitalElements&, double, double)`
  - Modular API (refactored):
    - `solve_kepler_elliptical(double, double)`
    - `solve_kepler_hyperbolic(double, double)`
    - `eccentric_to_true_anomaly(double, double)`
    - `hyperbolic_to_true_anomaly(double, double)`
    - `mean_anomaly_to_true_anomaly(double, double)`

- Added to `src/orbital_mechanics.cpp`: Full implementations
  - Newton-Raphson solver with 1e-10 tolerance, max 50 iterations
  - Series expansion initial guess: M + e*sin(M) + (e²/2)*sin(2M)
  - Cartesian to orbital elements conversion algorithm
  - Fixed: true_anomaly calculation with proper clamping (line 122)
  - Fixed: circular orbit velocity calculation (line 40-42)
  - Refactored: Separated elliptical/hyperbolic Kepler solvers
  - Refactored: Added inline comments to orbital_elements_to_cartesian()

- Removed from `src/test_utilities.h/.cpp`: `propagate_orbital_elements()`
- Added to `src/config_validator.cpp`:
  - `validate_true_anomaly_ranges()` - checks hyperbolic anomaly limits
  - TODO comment about parabolic tolerance (0.005 too broad)

**Bug Fixes:**
1. `cartesian_to_orbital_elements()` (line 122): Fixed true_anomaly calculation
   - Corrected formula: r_dot_e / (r_mag * e_mag) instead of r_dot_e / mu
   - Added clamping: cos(ν) clamped to [-1, 1] before acos()

2. `test_extreme_eccentricity.toml`: Fixed spacecraft parameters
   - "Near_Parabolic": e=0.99, a=7.0e8
   - "Slightly_Hyperbolic": e=1.05, a=-1.3e8

3. `test_extreme_eccentricity.cpp`: Added hyperbolic anomaly validation
   - Skips testing ν=π and 3π/2 for e>1 (outside asymptote boundaries)

4. `test_newton_raphson_convergence.cpp`: Fixed test expectations
   - Verifies Kepler's equation: |E - e·sin(E) - M| < 1.0e-10
   - Verifies first-order approximation: |E - (M + e·sin(M))| < 0.01

5. `test_analytical_propagation_apsides.cpp`: Fixed velocity comparison logic
   - Changed: Measure velocity at ν=π/4, compare to perigee velocity at ν=0
   - Before: Both measurements at ν=0 (same anomaly, meaningless comparison)

6. `test_analytical_propagation_timesteps.cpp`: Fixed 3 test design issues
   - Small timestep: Check position error instead of absolute position change
   - Division by zero: Check expected_pos_error > 1e-6 before calculating relative error
   - 2π wrapping: Use fmin(raw_error, 2π - raw_error) for angular error

7. `test_precision_boundaries.cpp`: Removed incorrect Z-coordinate check
   - Test expected Z = r·sin(i), which assumes motion along Z-axis
   - Actual position at perigee is on X-axis, so Z=0 is correct

8. `orbital_elements_to_cartesian()` (line 40-42): Fixed circular orbit velocity
   - Changed from constant velocity vx=0, vy=v_mag
   - To correct rotating velocity vx=-v·sin(ν), vy=v·cos(ν)
   - Angular momentum now properly conserved (1.2e-14% error instead of 41.4%)

**Test Results:** All 80 tests passing (239,555 assertions)

**Recent Commits:**
- 9d97934 Fix true anomaly calculation in cartesian_to_orbital_elements()
- a46291a Fix test_extreme_eccentricity to skip invalid hyperbolic true anomalies
- 47f156b Add true anomaly validation for hyperbolic orbits in config validator
- 01e5492 Refactor orbital_mechanics: separate elliptical and hyperbolic Kepler solvers
- 5fc7348 Fix test_analytical_propagation_apsides: measure velocity at different anomaly
- 7471d06 Fix test_analytical_propagation_timesteps: tolerance, division by zero, and 2π wrapping
- acfb47a Fix test_precision_boundaries: remove incorrect Z-coordinate check for polar orbit
 - 849a212 Fix orbital_elements_to_cartesian: circular orbit velocity and refactor for clarity
 - 986a94e Update test plan: document progress on 3 fixed test files

### Remaining Tests (8 files)

#### 7. ⬜ test_cartesian_to_elements_extreme.cpp + .toml
- Purpose: Edge cases in orbital parameters
- Config: Multiple spacecraft in same config
  - Near-circular (e=0.001)
  - Highly eccentric (e=0.99)
  - Equatorial (i<0.001)
  - Polar (i≈π/2)
  - Retrograde (i>π/2)
- Tests:
  - Numerical precision at boundary values
  - Degenerate Ω calculation for equatorial
  - Rotation singularities for polar

#### 8. ⬜ test_cartesian_to_elements_quadrature.cpp + .toml
- Purpose: Test calculations at orbital quadrature points
- Config: Spacecraft at true anomalies: 0, π/2, π, 3π/2
- Tests:
  - Cross product calculations at quadrants
  - Eccentricity vector accuracy
  - Position/velocity vector relationships

#### 9. ⬜ test_hybrid_impulse_burns.cpp + .toml
- Purpose: Impulsive burn handling
- Config: Spacecraft with pre-configured maneuvers
- Tests:
  - Hohmann transfer (2 burns)
  - Plane change at nodes (inclination change only)
  - Impulsive burns at apsides (perigee/apogee)
  - Minimal burns (Δv < 1 m/s)
  - Large burns (Δv > orbital velocity)

#### 10. ⬜ test_hybrid_continuous_thrust.cpp + .toml
- Purpose: Continuous thrust integration
- Config: Spacecraft with finite-duration burns
- Tests:
  - Continuous low-thrust burns (ion engines)
  - Multi-burn sequences
  - Numerical vs. analytical mode transitions
  - Energy conservation during burns

#### 11. ⬜ test_hybrid_energy_conservation.cpp + .toml
- Purpose: Compare analytical vs. numerical propagation
- Config: Same spacecraft propagated with both methods
- Tests:
  - Energy comparison: analytical vs. RK4
  - Pre/post burn energy validation
  - Long-term energy drift comparison

#### 12. ⬜ test_extreme_orientation.cpp + .toml
- Purpose: 3D orientation edge cases
- Config:
  - Polar orbit (i=90°)
  - Retrograde orbit (i=180°)
  - Mixed: high inclination + high eccentricity
- Tests:
  - Rotation matrix behavior at i=π/2
  - Ω and ω singularity handling
  - Z-coordinate preservation for polar
  - Velocity vector orientation

#### 13. ⬜ test_extreme_timescales.cpp + .toml
- Purpose: Orbital period extremes
- Config:
  - Mercury-like orbiter (period ~88 days)
  - Very long period orbit (period > 10 years)
  - Very low perigee (altitude < 100 km)
  - Super-synchronous orbit
- Tests:
  - Fast orbits: numerical precision challenges
  - Slow orbits: mean anomaly accumulation
  - Low altitude: atmospheric boundary (if applicable)
  - Long-duration propagation (10+ periods)

#### 14. ⬜ test_energy_conservation_analytical.cpp + .toml (OPTIONAL)
- Purpose: Long-term energy conservation validation
- Config: Standard circular/elliptical orbit
- Tests:
  - Energy drift over 10+ orbital periods
  - Kinetic/potential energy consistency
  - Vis-viva equation verification at all anomalies

## Phase 1: Core Math Functions

### Cartesian to Orbital Elements (3 files)

#### 1. test_cartesian_to_elements_basic.cpp + .toml
- Purpose: Basic round-trip conversion accuracy
- Config: Moderate eccentricity, zero inclination orbit
- Tests:
  - Round-trip conversion: orbital elements → state vectors → orbital elements
  - Position/velocity magnitude preservation
  - Semi-major axis, eccentricity accuracy

#### 2. test_cartesian_to_elements_extreme.cpp + .toml
- Purpose: Edge cases in orbital parameters
- Config: Multiple spacecraft in same config
  - Near-circular (e=0.001)
  - Highly eccentric (e=0.99)
  - Equatorial (i<0.001)
  - Polar (i≈π/2)
  - Retrograde (i>π/2)
- Tests:
  - Numerical precision at boundary values
  - Degenerate Ω calculation for equatorial
  - Rotation singularities for polar

#### 3. test_cartesian_to_elements_quadrature.cpp + .toml
- Purpose: Test calculations at orbital quadrature points
- Config: Spacecraft at true anomalies: 0, π/2, π, 3π/2
- Tests:
  - Cross product calculations at quadrants
  - Eccentricity vector accuracy
  - Position/velocity vector relationships

### Newton-Raphson Solver (1-2 files)

#### 4. test_newton_raphson_convergence.cpp + .toml
- Purpose: Verify convergence behavior across eccentricity ranges
- Config: Spacecraft with programmatically varied parameters
- Tests:
  - Very low eccentricity (e < 0.01): convergence rate verification
  - High eccentricity (0.9 < e < 0.99): iteration count limits
  - Mean anomaly near π: worst-case convergence
  - Large mean anomaly values (M > 1000): periodicity handling
  - Eccentricity at boundaries (e = 0.9999, 1.0001)
- Note: Could split to separate config if boundary cases need dedicated config

### Analytical Propagation (2 files)

#### 5. test_analytical_propagation_apsides.cpp + .toml
- Purpose: Propagation through orbital apsides
- Config: Elliptical orbit
- Tests:
  - Propagation through perigee (velocity maximum)
  - Propagation through apogee (velocity minimum)
  - At exact orbital period: should return to initial state
  - True anomaly accuracy after full orbit

#### 6. test_analytical_propagation_timesteps.cpp + .toml
- Purpose: Timestep size validation
- Config: Standard orbit
- Tests:
  - Large timesteps: dt > 1 orbit period
  - Very small timesteps: dt < 1 second
  - Accuracy vs. timestep size relationship
  - Mean anomaly accumulation over long propagation

## Phase 2: Hybrid Integration

#### 7. test_hybrid_impulse_burns.cpp + .toml
- Purpose: Impulsive burn handling
- Config: Spacecraft with pre-configured maneuvers
- Tests:
  - Hohmann transfer (2 burns)
  - Plane change at nodes (inclination change only)
  - Impulsive burns at apsides (perigee/apogee)
  - Minimal burns (Δv < 1 m/s)
  - Large burns (Δv > orbital velocity)

#### 8. test_hybrid_continuous_thrust.cpp + .toml
- Purpose: Continuous thrust integration
- Config: Spacecraft with finite-duration burns
- Tests:
  - Continuous low-thrust burns (ion engines)
  - Multi-burn sequences
  - Numerical vs. analytical mode transitions
  - Energy conservation during burns

#### 9. test_hybrid_energy_conservation.cpp + .toml
- Purpose: Compare analytical vs. numerical propagation
- Config: Same spacecraft propagated with both methods
- Tests:
  - Energy comparison: analytical vs. RK4
  - Pre/post burn energy validation
  - Long-term energy drift comparison

## Extreme Orbits (3 files)

#### 10. test_extreme_eccentricity.cpp + .toml
- Purpose: Near-parabolic boundary behavior
- Config:
  - Highly eccentric (e=0.99)
  - Near parabolic (e=0.9999, e=1.0001)
- Tests:
  - Numerical stability near e=1.0
  - Hyperbolic solver switching
  - Velocity magnitude accuracy
  - Period calculation (or lack thereof for e≥1)

#### 11. test_extreme_orientation.cpp + .toml
- Purpose: 3D orientation edge cases
- Config:
  - Polar orbit (i=90°)
  - Retrograde orbit (i=180°)
  - Mixed: high inclination + high eccentricity
- Tests:
  - Rotation matrix behavior at i=π/2
  - Ω and ω singularity handling
  - Z-coordinate preservation for polar
  - Velocity vector orientation

#### 12. test_extreme_timescales.cpp + .toml
- Purpose: Orbital period extremes
- Config:
  - Mercury-like orbiter (period ~88 days)
  - Very long period orbit (period > 10 years)
  - Very low perigee (altitude < 100 km)
  - Super-synchronous orbit
- Tests:
  - Fast orbits: numerical precision challenges
  - Slow orbits: mean anomaly accumulation
  - Low altitude: atmospheric boundary (if applicable)
  - Long-duration propagation (10+ periods)

## Numerical Precision (1-2 files)

#### 13. test_precision_boundaries.cpp + .toml
- Purpose: Exact boundary value handling
- Config:
  - Perfect circle (e=0)
  - Polar orbit (i=π/2)
  - Retrograde orbit (i=π)
  - Zero/very small radius or velocity
- Tests:
  - Eccentricity at exactly 0
  - Eccentricity at exactly 1 (parabolic)
  - Inclination at 0°, 90°, 180°
  - Semi-major axis sign change
  - Angular momentum conservation
- Note: If energy conservation needs separate config, this becomes 2 files

#### 14. (Optional) test_energy_conservation_analytical.cpp + .toml
- Purpose: Long-term energy conservation validation
- Config: Standard circular/elliptical orbit
- Tests:
  - Energy drift over 10+ orbital periods
  - Kinetic/potential energy consistency
  - Vis-viva equation verification at all anomalies

## Overlap Analysis with Existing Tests

### Existing Test Coverage Summary

**Orbital Parameters Currently Tested:**
- Eccentricity: e=0.0 (circular), 0.74 (Molniya), 1.0 (parabolic), 1.5 (hyperbolic)
- Inclination: i=0.0 (equatorial), 1.107 rad (63.4°, Molniya)
- Orbital Periods: 1 day, 10 days, 15.95 days (Titan), 27.3 days (Moon), 60 days, 365 days (Earth), 687 days (Mars), 300-2000 days

**Test Scenarios Currently Tested:**
- Energy conservation (RK4 only)
- Orbital period measurement
- Prograde/retrograde/normal impulsive burns
- Time-based and true anomaly triggers
- Inclined orbits (Molniya)
- Parabolic and hyperbolic orbits
- Moon orbital stability
- SOI transitions (deferred)
- Root body transitions (deferred)

**Overlaps Identified:**

**test_inclined_orbits.cpp** (Molniya: e=0.74, i=63.4°)
- Overlaps: Extreme eccentricity, Extreme orientation
- Gap: Need e=0.99+, retrograde (i>π/2), polar (i=π/2 exactly)

**test_moon_orbits.cpp** (Moon ~27 day period)
- Overlaps: Extreme timescales
- Gap: Need Mercury-like (~88 days), very slow (>10 years)

**test_energy.cpp** (circular orbit energy)
- Overlaps: Energy conservation tests
- Gap: Need analytical propagation validation, method comparison

**test_orbital_period.cpp** (Earth 365 days, Mars 687 days)
- Overlaps: Extreme timescales
- Gap: Need <10 days, ~88 days, >3650 days

**test_parabolic_orbit.cpp** (e=1.0)
- Overlaps: Extreme eccentricity
- Gap: Need e=0.99, e=0.9999, e=1.0001

**test_hyperbolic_orbit.cpp** (e=1.5)
- Overlaps: Extreme eccentricity
- Gap: Need e=0.9999 near-parabolic boundary

**test_maneuvers.cpp** (prograde/retrograde/normal burns)
- Overlaps: Hybrid impulse burns
- Gap: Need continuous thrust, Hohmann sequence, apsides burns

**test_maneuver_planning.cpp** (time/true anomaly triggers)
- Overlaps: Hybrid impulse burns
- Gap: Need burns at apsides, Hohmann transfer

### Config Sharing Opportunities

**Can Share Configs (Partial Overlap):**
1. **test_extreme_eccentricity** ↔ test_parabolic_orbit/hyperbolic_orbit
   - Existing: e=1.0, 1.5
   - New: e=0.99, 0.9999, 1.0001
   - May need new config for e=0.99, 0.9999 cases

2. **test_hybrid_impulse_burns** ↔ test_maneuvers
   - Can reuse burn infrastructure
   - New scenarios require separate config (Hohmann, apsides burns)

3. **test_hybrid_energy_conservation** ↔ test_energy
   - Different objectives (comparison vs. drift)
   - Could share circular orbit config

**Cannot Share Configs (Different Parameters):**
1. **test_extreme_orientation** vs test_inclined_orbits
   - Existing: i=1.107 (63.4°)
   - New: i=π/2 (90°), i>π/2 (retrograde)

2. **test_cartesian_to_elements_extreme** vs all existing
   - New test category (no existing tests)

### Unique New Test Categories

**Entirely New Functionality:**
1. Cartesian to orbital elements conversion (Phase 1.1) - 3 tests
2. Newton-Raphson solver convergence (Phase 1.2) - 1 test
3. Analytical propagation accuracy (Phase 1.3) - 2 tests
4. Hybrid continuous thrust integration (Phase 2.2) - 1 test
5. Energy comparison: analytical vs. RK4 (Phase 2.3) - 1 test
6. Propagation through apsides - 1 test

**New Orbital Regimes:**
7. Retrograde orbits (i > 90°) - 1 test
8. Extremely fast orbits (Mercury-like, <100 days) - 1 test
9. Extremely slow orbits (>10 years) - 1 test
10. Boundary values (e=0, i=π/2, i=π) - 1 test

### Minimal File Count with Sharing

**Current estimate: 13-14 files**

**Optimization opportunities:**
- Combine e=0.99 with parabolic/hyperbolic configs → -1 file
- Share energy config between test_energy and test_hybrid_energy_conservation → -1 file
- Use existing Molniya config for some extreme orientation tests → -1 file

**Optimized estimate: ~11 files**

**Recommended: Keep 13-14 files**
- Each test has self-documenting config
- Easier to debug isolated failures
- Config reuse doesn't save much (configs are small)
- Clear separation of concerns

## Implementation Priority

### Phase 1 (Foundation)
1. test_cartesian_to_elements_basic.cpp (round-trip conversion)
2. test_newton_raphson_convergence.cpp (solver validation)
3. test_analytical_propagation_apsides.cpp (basic propagation)

### Phase 2 (Hybrid Integration)
4. test_hybrid_impulse_burns.cpp (impulsive burns)
5. test_hybrid_continuous_thrust.cpp (continuous burns)
6. test_hybrid_energy_conservation.cpp (method comparison)

### Phase 3 (Edge Cases)
7. test_extreme_eccentricity.cpp (e≈1.0)
8. test_extreme_orientation.cpp (polar/retrograde)
9. test_extreme_timescales.cpp (fast/slow periods)
10. test_precision_boundaries.cpp (exact values)
11. test_cartesian_to_elements_extreme.cpp (edge cases)
12. test_cartesian_to_elements_quadrature.cpp (quadrants)
13. test_analytical_propagation_timesteps.cpp (large/small dt)

## Notes
- Config files are shared with existing tests where possible
- Each .cpp file requires corresponding .toml config
- Some test categories can share configs if parameters align
- SOI transition tests deferred per user requirements