PicSat: a CubeSat for beta Pictoris observation
Abstract
PicSat is a nanosatellite that was integrated and operated by the Paris Observatory to observe the transit of the giant planet Beta Pictoris b, expected to happen in 2018. The satellite has been successfully put into a 505 km Sun synchronous orbit in January (PSLV C-40). The mission is based on a 3U CubeSat architecture, with a 2 kg opto-mechanical payload specifically designed for high precision photometry. While the platform has been provided "off-the-shelf" by ISIS (Innovative Solutions In Space), the payload (hardware and software), the flight software and the ground segment/station have been mostly developed in-house at the Observatory. The main scientific objective of the mission is the nearly continuous monitoring of the brightness of Beta Pic at a precision of up to 200 ppm per hour, with interruptions of at most 30 minutes, caused by the eclipse of BetaPic by the Earth in some fraction of the satellite orbit. This setup will allow Picsat to finely characterize the debris disk, the transiting exoplanet, its gravitational surroundings (the Hill sphere) and to detect exocomets in the Pictoris system. The payload is a telescope with a 3.5 cm effective aperture which injects the light in a single-mode fiber linked to an avalanche photodiode, operating in the visible spectrum. A two-axis piezoelectric actuator system, driven by a feedback loop control algorithm based on a Kalman filter, is used to lock the fiber on the center of the star in the focal plane. These actuators complement the attitude determination and control system of the satellite to maintain the sub-arcsecond pointing accuracy required to reach the excellent level of photometric precision. Overall, the mission raises multiple technical challenges: high temperature stability of the avalanche detector (achieved with a thermoelectric cooling device), high pointing accuracy and stability, and short timeframe for the development. The mission is also a technological demonstrator. By showing that we can inject light into a single mode fiber, using only a small (1U) payload, we pave the way for a more ambitious cubesat: FIRST-S, an interferometer based on two injecting telescopes and a beam combiner using integrated optics.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E.771D