Near-Earth asteroids (NEAs) with perihelion distances under 1.3 AU pose potential impact risks to Earth, as exemplified by historical events like the Chelyabinsk meteor. While ground-based surveys such as the Catalina Sky Survey, Pan-STARRS, and ATLAS have discovered many NEAs, they face fundamental limitations due to atmospheric interference, daylight constraints, and inability to observe in the Sun-facing direction, which represents the approach direction of some potential impactors.

To address these challenges, we conduct a comprehensive performance evaluation of an infrared monitoring system deployed in an Earth-leading (EL) orbit at 0.1 AU ahead of Earth. We establish a visibility model that incorporates radiative transfer theory with the near-Earth asteroid thermal model (NEATM), which calculates temperature distributions as functions of phase angle and beaming parameter η. This improves upon earlier models that assumed constant surface temperature. The total flux—including reflected sunlight and thermal emission—is computed across wavelengths and expressed in μJy to facilitate comparison against typical a detection threshold of 150 μJy in the 6?10 μm infrared band. For comparative analysis, the H-G photometric phase function (H is absolute magnitude and G is slope parameter) is adopted to study the visibility model of the visible light band with a limit apparent magnitude of 24. During the six-year mission, three orbital deployments are simulated: single EL telescope, the Sun-Earth L1 point telescope, and the dual EL+Earth-trailing (ET) telescopes at ±0.1 AU around Earth. All systems implement strict Earth avoidance constraints (±5° longitude and latitude) and use the same observational cadences (30 s repointing and 180 s integration per 1.875°×7° field-of-view). Simulations employ 213284 synthetic NEAs (≥50 m diameter) from Granvik’s debiased population model, propagated under heliocentric two-body dynamics. Key performance indicators include catalog completeness (the ratio of asteroids that have been observed at least 4 times within 30 days to the total number of asteroids), warning rate (the ratio of the number of asteroids that have entered the 0.05 AU range around the Earth and have been discovered before their perigee to the total number of asteroids that have actually entered the 0.05 AU range), and the Sun direction warning rate (the warning rate of asteroids entering within 0.05 AU of the Earth from the direction of the Sun). Simulation results show that thermal emission dominates over reflected light in the mid-infrared, especially for low-albedo asteroids and those approaching from the direction of the Sun, making infrared observations particularly effective.

Simulations map detection boundaries for 20-m, 50-m, and 140-m NEAs in heliocentric coordinates (Fig. 9). At 150 μJy sensitivity, maximum detection distances vary significantly with observing geometry: 20-m NEAs are detectable to 0.18 AU, dropping to 0.1 AU at high phase angles where cold non-illuminated surfaces dominate. For 50-m NEAs, ranges extended to 0.35 AU in sunward directions and peaked at 0.45 AU near 100° phase angle-confirming infrared (IR) superiority for solar approaches. Reducing sensitivity to 1000 μJy severely degrade Sun-side performance (e.g., 50-m range at 45° phase fell from 0.4 AU to 0.07 AU), while anti-Sun detection is less affected. This demonstrates IR sensitivity’s critical role for blind-zone monitoring. Crucially, the EL telescope configuration dedicated to solar quadrants (EL 1: longitude between [-45°,0]) achieves 86.88% Sun-direction warning rate—a 14-percentage-point absolute improvement over L1’s 72.93% (Table 2). This is because its field of view directly faces the Sun on the Earth’s side, effectively covering potential Sun-side threat areas. When expanding the EL field to ±45° (EL 2 configuration), catalog completeness increases to 37.97% but solar warning decreases to 75.83% due to reduced Sun-focused observation time. The dual EL+ET system operating at ±45° ecliptic longitude demonstrates unprecedented synergy: catalog completeness reaches 52.77% while Sun-direction warning achieves 91.50%—the highest among all configurations (Table 4). This performance emerges from continuous coverage of Earth’s approach corridors, enabling earlier detection of objects. Temporal analysis reveals that the EL+ET system maintains more than 50% catalog completeness for 50-m NEAs throughout the 6-year mission, matching L1’s performance (Fig. 11).

In summary, this study compares different orbital configurations for space-based infrared monitoring of NEAs and identifies two configurations with notable advantages. First, EL orbits provide strong Sun-direction warning capability—achieving 86.88% with a single telescope—by covering regions that ground-based systems cannot observe. Second, a dual EL+ET system further improves overall performance, reaching 91.50% Sun-direction warning and 52.77% catalog completeness, enabling both early warning and effective population tracking. While L1 orbits offer engineering benefits such as thermal stability and simplified station-keeping, the EL+ET configuration is more effective for detecting objects approaching from the Sun direction. The infrared telescope deployed in an EL orbit demonstrates clear advantages in early detection of NEAs, particularly those approaching from the Sun direction. The developed model and simulation framework provide quantitative support for the architectural design of future space-based planetary defense missions.