Extended Mission Technology Demonstrations Using the ASTERIA Spacecraft Lorraine Fesq, Patricia Beauchamp, Amanda Donner, Mary Knapp Rob Bocchino, Brian Kennedy, Swati Mohan, David MIT Haystack Observatory Sternberg, Matthew W. Smith, Martina Troesch 99 Millstone Rd. Jet Propulsion Laboratory, California Institute of Westford, MA 01886 Technology (607) 425-9617 4800 Oak Grove Dr. [email protected] Pasadena, CA 91109 (818) 393-7224, 354-0529, 393-8636, 354-8175, 354- 6327, 354-5305, 354-6685 354-1319, 354-8088 {Lorraine.M.Fesq, Patricia.M.Beauchamp, Amanda.Neufeld, Robert.L.Bocchino, Brian.M.Kennedy, Swati.Mohan, David.C.Sternberg, Matthew.W.Smith, Martina.I.Troesch}@jpl.nasa.gov Abstract— ASTERIA (Arcsecond Space Telescope Enabling be our closest exoplanetary neighbor orbiting a Sun- Research In Astrophysics) is a CubeSat space telescope like star. currently operating in low-Earth orbit. It is expected to remain in orbit at least through October 2019. Developed as a These demonstrations will provide in-flight testing of new technology demonstration mission under the JPL Phaeton autonomy technologies, maximize the scientific potential of this Program for training early-career engineers, ASTERIA has operational spacecraft, and provide additional characterization achieved sub-arcsecond pointing stability and milliKelvin of hardware for future small satellite missions using similar thermal stability over 20-minute observations. These subsystems. capabilities—unprecedented in a CubeSat platform—have enabled photometric precision better than 1000 ppm/min while TABLE OF CONTENTS observing nearby bright stars (V<6). 1. INTRODUCTION ....................................................... 1 Following the second extended mission, we are now using the 2. BACKGROUND ......................................................... 2 spacecraft in its third extension as a platform to demonstrate additional capabilities as well as continue science observations. 3. EXTENDED MISSION ACTIVITIES ........................... 4 This project will perform the following four well-focused 4. SUMMARY ................................................................ 8 activities that will raise the technology readiness of key ACKNOWLEDGEMENTS .............................................. 9 spacecraft technologies. REFERENCES ............................................................... 9 1. Shift the paradigm to operate spacecraft from open- BIOGRAPHIES .............................................................. 9 loop commanding to closed-loop command execution: We will introduce “task networks” (tasknets) which 1. INTRODUCTION allow simpler commanding and more robust on- board execution. ASTERIA (Arcsecond Space Telescope Enabling Research 2. Demonstrate onboard orbit determination in Low In Astrophysics) is a CubeSat space telescope currently Earth Orbit (LEO) using autonomous navigation operating in low-Earth orbit. It is expected to remain in orbit (Autonav) without GPS: This activity will demon- through at least October 2019. Developed as a technology strate a fully independent means of spacecraft orbit determination for Earth orbiters using only passive demonstration mission under the JPL Phaeton Program for imaging. training early career engineers, ASTERIA has achieved sub- 3. Collect data on ASTERIA that will feed into future arcsecond pointing stability and milliKelvin thermal missions by characterizing the spacecraft pointing jit- stability over 20-minute observations [1][2]. These ter as a function of target brightness, reaction wheel capabilities—unprecedented in a CubeSat platform—have speed, controller gain, and number of guide stars. enabled photometric precision better than 1000 ppm/min 4. Perform ASTERIA extended mission science: while observing nearby bright stars (V<6). ASTERIA has demonstrated unprecedented photo- metric precision for a CubeSat mission. The space- JPL now has extended the ASTERIA mission beyond its craft is uniquely suited to perform long-term moni- prime mission and two short extended missions to build on toring of stars such as alpha Centauri for small trans- iting planets. The discovery of a transiting Earth- ASTERIA’s outstanding science results and to perform four sized planet around alpha Cen A and/or B would be targeted activities that will raise the readiness of key of the highest scientific value as such a planet would technologies. Specifically, the extended mission aims to achieve the following: 978-1-5386-6854-2/19/$31.00 ©2019 IEEE 1 1. Shift the paradigm to operate spacecraft from open- 90-day primary mission. As of 1 February 2018, the mission loop commanding to closed-loop command execu- satisfied Level 1 Requirements by achieving the following tion. Introduce task networks (“tasknets”) to allow milestones: simpler commanding and more robust on-board execu- tion. ASTERIA will continue to carry out scientific • Demonstrating optical line-of-sight pointing stability of observations to demonstrate the effectiveness of these 0.5 arcsecond RMS over 20 minutes (compared to the tasknets and the applicability of this approach for requirement of 5 arcseconds). increasing the efficiency and robustness of future space missions. • Demonstrating focal plane temperature stability better 2. Demonstrate onboard orbit determination in Low than ±10 milliKelvin over 20 minutes. Earth Orbit (LEO) using autonomous navigation (“Autonav”) without GPS. This activity will demon- • Demonstrating the ability to collect windowed images strate a fully-independent means of spacecraft orbit and produce stellar flux data in a cadence that permits determination for Earth orbiters using only passive photometric study of nearby bright stars. imaging. This capability will enable future missions to navigate in GPS-denied environments and with a more The level of pointing and thermal control obtained by robust sensor suite. ASTERIA is unprecedented compared to other missions in a 3. Collect data on ASTERIA that will feed into future similar mass category (see Figure 1 and Figure 2). missions. Characterize the spacecraft pointing jitter as a Recent processing of data obtained during the mission so far function of target brightness, reaction wheel speed, has demonstrated the capability to detect the known transit controller gain, and the number of guide stars. These of 55 Cancri e, a super-Earth exoplanet (2 R ) orbiting a data will yield additional insights into the contribution Earth nearby bright Sun-like star (V = 5.95). ASTERIA’s of jitter to the ASTERIA photometry and inform the photometric precision is of sufficient quality that this 410 feasibility of other astrophysics small satellite missions ppm transit was detected at a significance of 3σ (see Figure for which jitter control is an enabling technology. 3) [3]. This marks the first time that a CubeSat has observed 4. Perform ASTERIA extended mission science. an exoplanet transit and offers a proof of concept that ASTERIA has demonstrated unprecedented photomet- meaningful astrophysical measurements—including ric precision for a CubeSat mission. The spacecraft is exoplanet detections—are feasible using a CubeSat uniquely suited to perform long-term monitoring of platform. stars such as alpha Centauri for small transiting planets. The discovery of a transiting Earth-sized planet The scientific objective of the current mission is to conduct around alpha Cen A and/or B would be of the highest opportunistic observations for the detection of small scientific value as such a planet would be our closest transiting exoplanets (one to several Earth radii) by exoplanetary neighbor orbiting a Sun-like star. observing HD 219134 and the alpha Centauri system. Additional observations also can be achieved including Transits of small exoplanets are not detectable from the targeting other spacecraft and performing Earth Science ground due to the blurring effects of Earth’s atmosphere but weather phenomena imaging. With additional funding they offer rich science potential. Transit light curves offer a and a further extension, the spacecraft could be pro- direct measurement of exoplanet radius, constraining grammed to detect and respond to transient events. planetary composition. Small planets transiting bright, nearby stars are the best candidates for follow-up atmospheric characterization via transit spectroscopy by These activities will interleave with one another to exploit other observatories (e.g. HST, JWST). the use of the spacecraft over the timeframe of the extension. In addition to maximizing the scientific potential ASTERIA’s main target is HD 219134, a nearby star with of this operational spacecraft, this extension will provide two known transiting exoplanets, designated b and c [4]. additional context for future small satellite astrophysics This system is compelling for ASTERIA because it hosts missions. These missions include (1) missions considered two additional exoplanets not known to transit. Designated under NASA’s Astrophysics Science SmallSat Studies d and f, these planets were discovered by radial velocity solicitation (NNH18ZDA001N-AS3) and (2) missions measurements and are small “mini Neptune” planets in 22- considered under NASA’s recent AO for Astrophysics and 46-day orbits respectively [5]. ASTERIA has observed Explorers. The AO includes Missions of Opportunity for time windows corresponding to the possible d and f transits. CubeSats/SmallSats (NNH18ZDA014L). Data from those observations are currently being analyzed by the science team to determine whether a transit of