How NASA's Psyche Mission Captured Mars During a Gravity Assist: A Step-by-Step Guide

Overview

In May 2026, NASA's Psyche spacecraft performed a critical gravity assist maneuver around Mars, using the planet's gravitational pull to gain speed and adjust its trajectory toward its final destination: the asteroid Psyche. As part of this flyby, the mission's multispectral imager captured a stunning colorized image of Mars from approximately 3 million miles (4.8 million kilometers) away. This guide breaks down the science, planning, and execution behind that image, turning a real mission event into a practical tutorial for understanding high-phase-angle imaging, gravitational assists, and planetary observation techniques.

By the end of this guide, you'll understand how the Psyche team prepared for the image, why Mars appeared as a crescent, and the role of dust and seasonal clouds in shaping the final picture. We'll also cover common pitfalls in such imaging exercises.

Prerequisites

To get the most out of this tutorial, you should be familiar with:

• Basic concepts of orbital mechanics (gravitational slingshots, trajectories)
• Fundamentals of digital imaging (exposure, dynamic range, filters)
• Planetary science terminology (phase angle, albedo, atmospheric scattering)
• Familiarity with reading NASA mission press releases and image data

No coding or advanced math is required, but a curious mind about space exploration will help.

Step-by-Step Instructions for Recreating the Imaging Process

Follow these steps to understand how the Psyche mission captured Mars during the gravity assist approach. While you won't operate the actual spacecraft, these steps simulate the planning and analysis workflow.

Step 1: Plan the Gravity Assist Trajectory

The Psyche mission launched in 2023 and needed a boost to reach the asteroid Psyche in 2029. Engineers designed a Mars gravity assist that would use the planet's gravity to increase the spacecraft's velocity and bend its path. The trajectory placed the spacecraft on an approach that would bring it within a few million kilometers of Mars on May 3, 2026, with the closest approach on May 15. Key parameters: approach from a high-phase angle (the angle between the Sun, Mars, and the spacecraft), which means the Sun is behind the spacecraft from Mars's perspective, illuminating only a thin crescent of the planet.

Step 2: Calibrate the Multispectral Imager

The Psyche spacecraft carries a multispectral imager capable of capturing images in multiple filters, including a panchromatic (broadband) filter. Before the Mars flyby, the imager team conducted calibration tests to ensure the camera would function correctly during the high-speed approach. They set the exposure time to a mere 2 milliseconds—extremely short to prevent oversaturation from the bright Martian surface and atmospheric scattering.

Step 3: Acquire the Image at the Right Moment

On May 3, 2026, about 3 million miles from Mars, the spacecraft executed a pre-programmed observation sequence. The imager used the panchromatic filter with a 2 ms exposure. Because the spacecraft was approaching Mars from a high-phase angle, the image captured only a thin crescent of Mars, similar to a new Moon as seen from Earth. The Sun was out of frame, above both Mars and the spacecraft. The short exposure was intended to avoid saturating the detector, but even so, parts of the crescent were oversaturated due to the intensity of sunlight reflecting off Mars and scattering through its dusty atmosphere.

Step 4: Process and Colorize the Raw Data

After acquisition, the raw image data was transmitted to Earth. The imager team processed it using standard calibration routines (dark frame subtraction, flat fielding) to remove noise. For the colorized version (Figure A in the original release), they combined data from different filters or used a false-color technique to highlight surface features and atmospheric phenomena. The result shows Mars as a bright crescent against a dark space background, with no stars visible (they are too dim relative to the reflected light).

Step 5: Analyze Dust Scattering and Seasonal Effects

One of the most interesting aspects of the image is how Mars's thin atmosphere scatters sunlight, making the crescent appear to extend farther around the planet than would be expected from a body without an atmosphere (like our Moon). The team noted a gap on the right side of the extended crescent coinciding with the north polar cap, which was in winter at the time. They hypothesized that seasonal clouds and hazes in that region were blocking the atmospheric dust's ability to scatter sunlight. This analysis helps refine models of Martian atmospheric dynamics.

Step 6: Use the Images for Calibration and Practice

The primary goal of these images was not scientific discovery but calibration. By imaging a known target (Mars) under challenging lighting conditions, the team could characterize the imager's performance in flight—detecting any stray light, dynamic range issues, or artifacts. This practice run will be invaluable when the spacecraft approaches asteroid Psyche in 2029, where the lighting and geometry will be different but equally demanding.

Common Mistakes in High-Phase-Angle Imaging

Even seasoned mission teams encounter pitfalls. Here are some common ones—and how the Psyche team avoided them:

• Oversaturation due to underestimating brightness: The team correctly anticipated that Mars would be extremely bright, setting a 2 ms exposure. However, the dustiness of the atmosphere made the crescent even brighter than predicted, leading to some oversaturation. Mist to avoid: not accounting for atmospheric scattering in brightness models.
• Ignoring seasonal variability: Mars's dust content changes rapidly. The north polar cap's winter clouds blocked scattering in that region, creating a gap in the crescent. Mist: assuming uniform atmospheric conditions. Always check seasonal forecasts.
• Forgetting to calibrate with a known target: The team used Mars specifically because its properties are well understood. Mist: trying to calibrate an unknown instrument on an unknown target. Always use a reference body first.
• Expecting dim background stars: The image shows no stars because they were vastly dimmer than the Martian crescent. Mist: setting exposure to catch stars—it would wash out the planet. Separately image stars in a different orientation.

Summary

This guide walked through how NASA's Psyche mission captured and analyzed a colorized image of Mars during a gravity assist approach. We covered the trajectory planning, imager calibration, acquisition with a 2 ms exposure, processing to highlight the crescent shape, and analysis of dust scattering and polar cloud effects. The image serves both as a calibration milestone and a demonstration of the challenges of high-phase-angle imaging—oversaturation, atmospheric variability, and the importance of using known targets. By following these steps, you can better understand how deep-space missions use planetary flybys to test their instruments and refine their operations for primary science targets.