Survey and Operations
Contents
Sample Selection
Orbit
Operations
The ARRAKIHS mission is set to span three years, focusing on capturing data from approximately 50 square degrees annually. It will operate at incredibly low surface brightness levels using both visible and infrared bands, making it an exciting venture into the world of astronomical exploration. The mission aims to explore stellar streams and satellite galaxies around Milky Way analogs, providing key insights into the behavior of dark matter and testing the Λ-Cold Dark Matter (ΛCDM) model.
Achieving deep imaging at such low surface brightness levels from the ground is challenging due to atmospheric interference. To address this, ARRAKIHS will utilize a binocular telescope system aboard a mini satellite in Low Earth Orbit. This innovative approach will enable the mission to reach unprecedented surface brightness levels, achieving a minimum of 30 mag/arcsec² in visible wavelengths.
By operating in space and combining its unique orbit with an advanced observational strategy, ARRAKIHS will overcome the limitations of ground-based imaging, paving the way for a transformative exploration of faint stellar streams and satellite galaxies.
Sample Selection
The ARRAKIHS galaxy sample focuses on Milky Way-type systems, selected based on a combination of volume- and magnitude-limited criteria. Observed galaxies will be chosen to ensure their halos are fully captured within the field of view, enabling the detection of faint stellar streams and satellite galaxies. Additional observational constraints, such as minimizing zodiacal light and galactic plane extinction, will help maximize data quality. The final sample is being refined to support the mission’s evolving science goals.
ARRAKIHS Orbit
ARRAKIHS will operate in a low Earth, Sun-Synchronous Orbit (SSO) at an altitude between 650 and 800 km, providing stable thermal conditions and optimal visibility for its targets. The spacecraft, weighing 600 kg, will observe at an angle 60 degrees off-pointing with respect to the zenith. This orbit allows for efficient observations and cost-effective operations. Each galaxy will be observed using a series of 10-minute dithered exposures, with total observation times tailored to ensure the depth needed for detecting low surface brightness features. The mission’s nominal duration is three years.
Instrument Operations
The ground segment of a space mission includes all the Earth-based components that help manage the spacecraft, receive, process, archive and distribute its data. Key elements of this ground segment are the ground stations that communicate with the spacecraft and the mission control center where the spacecraft is managed. Additionally, it includes the computational structure to process the collected raw data, the software to produce and archive the final scientific images, as well as specific tools for calibrating periodically the instrument(s) embarked. These components ensure smooth operation and data sharing for the ARRAKIHS mission, and they will be operated by different organizations within AMC.
