Petrovascope

The Petrovascope is a specialized telescope aboard the Hail Mary designed to detect the 25.984-micron infrared light emitted by Astrophage, known as the Petrova wavelength. It is the ship's primary instrument for observing the Petrova line, the migration path of Astrophage between a star and its carbon-dioxide-rich planet, and for detecting other Astrophage-powered spacecraft. Its critical limitation is that it cannot be used while the ship's spin drive is active, because the engine's own immense infrared output would overwhelm its sensitive sensors, making it a tool that is both essential and, at crucial moments, unusable.

Design and Function

The Petrovascope is a finely tuned instrument that can detect even the smallest amounts of the Petrova wavelength. It is so sensitive that it must protect itself from the star it is observing; a physical metal plate is kept between its sensors and the star at all times to prevent damage from the star's overwhelming light at all wavelengths. When Grace first uses it in the Tau Ceti system, the screen shows a solid black circle with a hazy ring of light around it, which is the back of that protective plate. The instrument can be toggled between a "Visible" mode, which shows a standard visible-light view, and a "Petrova" mode, which shows only the Petrova wavelength. The interface allows the user to pan, zoom, and rotate the view.

Operational Limitation

The Petrovascope cannot be used while the spin drive is active. Grace deduces the reason: the spin drive consumes 6 grams of Astrophage per second, converting that mass into pure energy and emitting it as infrared light. This output is 540 trillion watts, an amount of energy considerably more than the surface of the sun. Any dust particles or ions between the ship and Tau Ceti would be vaporized by this blast, scattering some infrared light back at the ship. While this scattered light is negligible compared to the engine's output, it would be blinding to the Petrovascope, which is finely tuned to look for trace amounts of that exact frequency. This limitation means Grace cannot use the instrument to search for a Petrova line at Tau Ceti until the ship's deceleration burn is complete.

Key Uses in the Narrative

Once the spin drive is shut down and the ship is in orbit, Grace activates the Petrovascope and immediately confirms that Tau Ceti has a Petrova line, a beautiful dark-red arch coming out of the star. This is the first major piece of evidence that the mission is not in vain. The instrument then reveals the presence of an alien spacecraft, the Blip-A, which appears as a steady light source on the Petrova frequency. Grace uses the Petrovascope to observe the Blip-A's movements and to communicate with its occupant, Rocky, by flashing the Hail Mary's own engines in a pattern that the alien ship then mimics. Later, Grace uses the Petrovascope to locate the breeding altitude of Astrophage on the planet Adrian, identifying the specific layer of the atmosphere where the Astrophage emit their characteristic infrared light during reproduction. This discovery is crucial for planning the sampling mission. Finally, after rescuing Rocky, Grace uses the Petrovascope to track the Blip-A's engine flare as a beacon, allowing him to navigate back to the derelict ship.