GTOSat: A Pathfinder for a Smallsat-Based Operational Space Weather Program (And we do science!) Larry Kepko1, Lauren Blum1, Drew Turner2 and Alison Jaynes3 1NASA GSFC, 2The Aerospace Corporation, 3University of Iowa Strong desire & need for a space weather program 2012 Decadal Survey for Heliophysics recommended a space weather program “A vision for space weather and climatology” at $100-200M / year That program has not materialized Small satellites (<ESPA) have potential to achieve that goal RBSP / Van Allen Probes Revolutionized our understanding of Earth’s radiation belts, but 2 issues: 1. Limited radial distance - missed outer zone dynamics beyond L~5.5 2. It’s run out of fuel (decommission <early 2020) GTOSat is ready to fill those gaps Acceleration locations were sometimes beyond RBSP’s apogee μ = 735–765 MeV/G Boyd et al. (2018) Schiller et al (2013) Geosynchronous Transfer Orbit Satellite (GTOSat) Robust, low-cost cubesat with flight proven instruments for space weather and high quality science • Selected in H-TIDeS 2018 - 6U CubeSat, $4.35M total budget (including 1-year ops) - Designed to study the dynamics of outer belt electrons (science goal) - Explicitly a SmallSat space weather & constellation pathfinder - Confirmed CSLI selectee, working launch to GTO in early 2021 - Working with both JSC and KSC/LSP on de-orbit options - current baseline is passive - SRR 10/31/18, CDR 7/18/19, PSR 10/21/20 Carrying 2 instruments (MagEIS & Mag) that are on Van Allen Probes Leverages GSFC Dellingr experience (16 months and counting), combined with internal investments in C&DH and in-house SmallSat capability, and commercial solutions. GTOSat primary science objective Quantitatively understand the energy and pitch angle dependent dynamics of electrons in the outer radiation belt Observational Goals Measure pitch angle distributions (PADs) in differential energies through the outer radiation 1 belt 2 Measure electron phase space density profiles through the outer radiation belt 3 Measure energetic electron injections into the magnetosphere (within GEO) Jaynes et al. [2015] GTOSat carries MagEIS (REMS) Note energy dependent dynamics - that GTOSat will also see • Instrument lead: Drew Turner (Aerospace Corp) • Miniaturized version of the MagEIS instrument onboard NASA’s Van Allen Probes mission • Measures ~200 keV-2 MeV electrons, 10 differential energy channels (360 using histogram data) • Baselining 2 additional proton detectors, ~100 keV-8 MeV GTOSat carries a flight-proven magnetometer • Instrument lead: Jared Espley & Dave Sheppard (NASA GSFC Planetary Sciences) • Miniaturized version of magnetometers on MAVEN, Juno, PSP, Van Allen Probes Sun 1.0 4 segment boom, total length ~1 meter Sensor Observatory Overview Reaction IMU Fine Sun Wheels Sensors Avionics Stack Magnetometer Boom Batteries Patch Antenna & Radio (NEN & TDRSS) REMS (MagEIS) Flight Software is Core Flight - same as on MMS, GPM, PACE, etc. Concept of Operations Sun-pointed spinner (like RBSP). Keeps power positive, and enables PADs Magnetotorquers dump momentum inside L ~3 High rate downlink (1 Mbps) to NEN at perigee (~2x/day) *TDRSS low-latency space weather monitoring * Note on real-time beacon. TDRSS has limited FOV, still analyzing link budget for larger L shells. We’re looking at closing link via NEN for critical events. The CubeSat architecture permits shielding sample ionizing dose behind 3 g/cm2 shielding will originate characterizations with an infinite slab shielding from proton radiation. approximation approach, Figure 5. The calculations to determine approximate energies versus incident angles were critical in defining a working research payload architecture within the constraints of the CubeSat GTOSat has multi-prongedresearch pa yapproachedload surface area. A lar gtoe sh ieldhandleing test theA. radiation environment sample area, supporting the required large field of views, enable wide angle incidence of space radiation onto planned test samples of varying areal densities, enabling the infinite slab shielding approximation. Need to be here 25 krad B. Figure 5: Setup as an infinite slab approximation with 6 g/cm2 Al backing, promoting a repeatable experimental design with samples of varying thicknesses. Expected Results and Discussion: These shielding experiments are designed for GTO, where radiation levels are sufficient to build dose depth • Vault reduces total 1-year dose cutorv <es 25up to krad 3 g/c m2, which is a typical vault areal • Z-shielding material developedden bysity .NASA The GT OLaRC used fobaselinedr radiation m ofordeli n5g in Shieldose-2 and SPENVIS MULASSIS (Figure 6A and spacecraft walls (80 mil) 6B.) was 23° inclination, 37,500-km apogee, and 240- • Baseplate 150 mil Aluminum km perigee using the AP8min-AE8 Max Model Environment over a year period. In figure 6A, the • In house rad-hard C&DH systemex p ected ionizing dose of 10-400 MeV protons shows Figure 6 A. and B SPENVIS: Ionizing dose from • Extensive commercial research Aandl/TA outreachhas similar s hidentifiedielding perfo rmance to Al at AP8min-AE8 Max Model for GTO using approximately half the thickness. In figure 6B, the MULASSIS with propagated integration error from subsystems to meet the 25 krade xrequirementpected ionizing do se of 4-6.5 MeV electrons shows the dosimeter as a function of areal density for greater than 30% improvement in shielding planned Al, Ta, and Al/Ta samples. A. Proton effectiveness for Al/Ta over Al. Ionizing Dose. B. Electron Ionizing Dose. Ray trace studies confirm T~20he p rkradedomin aTIDnt rad foriatio n1 d-oyearse rec eived behind the mission, 95% AP/AE-s9,hield usinging sam p150les o rmiliginated Al from the proton ionizing dose. In figure 6A, the dose levels appear below 1 The Al/Ta Z-grade offers a thickness reduction kRad for Al and Al/Ta at areal densities above 1.7 2 g/cm2, whereas Ta appears higher. In figure 6B, the approaching half of a typical 3 g/cm (1.1 cm) Al electron radiation dose at areal densities above 1.7 shield. With CubeSat dimensions for a 1U at 3) g/cm2 appear below 200 Rad for Al/Ta and Ta. At areal approximately 10 cm x 10 cm x 10 cm (1000 cm , the densities greater than 2 g/cm2, the electron ionizing loss of electronics card volume area and cable volume 3 dose for the Al/Ta appears to be reduced almost would be 295 cm or ~30% of the 1U volume. A completely. Overall, the expected accumulated total shielding thickness of a 0.5 cm Z-grade would only Thomsen 5 29th Annual AIAA/USU Conference on Small Satellites GTOSat’s Contribution to Space Weather Monitoring GTOSat will measure • Electrons ~200 keV-2 MeV (10 differential energy channels) • Protons ~100 keV-8 MeV (TBD differential energy channels) GTOSat planned data products Mag REMS NOAA/SWPC Real-time* L1 DMPA coordinates Counts vs. time USAF/SWAFS Minutes after NEN L2 GSE and calibrated Intensity vs energy and time GSFC/iSWA+SWRC L3 Intensities vs. pitch angle and time, L* Few months CDAWeb Summary • GTOSat is a low-cost ($4.35M) 6U CubeSat designed to study electron dynamics in the outer radiation belts - Carries 2 Van Allen Probe instruments (MagEIS/REMS & magnetometer) - Will provide radiation belt measurement continuity with RBSP, while extending radial coverage. - ~200 keV-2 MeV electrons, 10 differential energy channels - ~100 keV-8 MeV protons, TBD differential energy channels • Demonstrates an operational space weather capability on a 6U platform. - Low-latency TDRSS and/or NEN support for critical events • Also represents a leap forward for constellations of spacecraft. - In particular MagCon and other transition region missions. GTOSat is a pathfinder for reliable, capable SmallSats beyond LEO .