A Sat-to-Sat Inspection Demonstration with the AeroCube-10 1.5U CubeSats

In the summer of 2020, the pair of AeroCube-10 1.5U CubeSats completed a series of mutual proximity operations as close as 22 meters separation and captured several sets of satellite-to-satellite resolved imagery, inspecting all faces of a vehicle in each pass with a resolution less than 8 mm. AeroCube-10 was designed and built by The Aerospace Corporation with the primary missions of atmospheric science and the maturation of nanosatellite technologies, including a new star tracker design, warm-gas propulsion system, GPS receiver, and a low-noise focal plane. Investigating the possibility of using CubeSats for satellite inspection missions, the AeroCube-10 team designed an experiment using these technologies in ensemble to bring the vehicles close together and demonstrate the feasibility of inspection missions in a package as small as 1.5U. Starting from a separation of more than one thousand kilometers, over the course of several weeks maneuvers executed with the AeroCube-10 propulsion unit brought the vehicles closer together, using proven formation keeping techniques to ensure safety of flight as the range dropped below 100 meters. The first imagery while in a natural-motion circumnavigation (NMC) was performed at a range of 64 meters. Gaining confidence in AeroCube-10’s capabilities, the operations team decreased the size of the NMC several times, obtaining imagery at 30 meters and then 22 meters. AeroCube-10 completed roughly one fourth of an NMC during each imaging run, and the observing satellite collected images of all faces of the target as it orbited around. At such close range, the inspection images clearly show individual solar cells, patch antennas, the exposed atmospheric probe magazine payload, the satellite’s miniature radiation dosimeter, and other features. AeroCube-10\u27s activities have demonstrated for the first time the feasibility of prolonged inspection activities in a very small form factor and, by closing from great distance and then entering NMC, proved that the nanosatellite platform has the potential for multiple-target inspection, as may be necessary for space-debris removal or constellation-inspection missions

The DiskSat: A Two-Dimensional Containerized Satellite

A key factor in the remarkable expansion of the CubeSat class of spacecraft over the past two decades is launch containerization. The container protects the launch vehicle and primary payload from issues that might arise from the CubeSat (which is essential for rideshare), and the standardized and highly-simplified launch interface reduces integration cost for the launch provider and development cost for the CubeSat builder. The downside of containerization is that the size of the contained satellites is rigidly limited. While there are available designs for larger dispensers and CubeSats, very few CubeSats larger than 6U have flown, and none have been larger than 16U. Future space missions will benefit from more power and RF aperture, beyond what can be provided by conventional CubeSats, even with complex deployables. We propose here the DiskSat, a containerized, large-aperture, quasi-two-dimensional satellite bus architecture. A representative DiskSat structure is a composite flat panel, one meter in diameter and 2.5 cm thick, to which components are affixed in a flat pattern within the panel. The volume of the representative DiskSat is almost 20 liters, comparable to a hypothetical 20U CubeSat, while the structural mass can be less than 2.5 kg. The surface area of a single disk face is substantially larger than the total surface area of any conventional CubeSat, supporting over 200 W of peak solar power without the complexity of deployables, thereby improving mission assurance and reducing vehicle cost. Alternatively, a single fixed deployable panel can ensure that the vehicle has over 100 W orbit-average power while maintaining nadir pointing in any beta angle. For launch, multiple DiskSats are stacked in a fully-enclosed container/dispenser using a simple mechanical interface, and are released individually once in orbit. Stacking of 20 or more DiskSats is possible in small launch vehicles, making it ideal for building large constellations of small satellites in multiple discrete orbital planes. The 1-m-diameter DiskSat was developed with the Rocket Lab Electron in mind; the concept can be extended to larger diameters (1.2 m for the Virgin LauncherOne, for example), or to other flat shapes (square for an ESPA port, for example), and to greater thicknesses if the mission requires it. The DiskSat concept was developed as a cost-effective solution for a LEO constellation that required significant power and RF aperture. Since then we have explored the utility of the bus architecture for a broad range of missions including Earth observation and space science, among others. One particularly useful feature of the DiskSat is the high power-to-mass ratio, enabling high-delta-v electric propulsion missions, including deep-space applications. Another feature is the ability to fly in a low-drag orientation which, in combination with electric propulsion for drag makeup, enables flight at very low altitudes in LEO. This paper will detail the design of the DiskSat and its dispenser, will explore the range of missions enabled by the DiskSat, and will describe current development activities in support of a DiskSat demonstration flight

Small Satellite Reliability Initiative (SSRI) Knowledge Base Tool: Use Case Review and Future Functionality and Content Direction

The Small Satellite Reliability Initiative (SSRI) Knowledge Base is a comprehensive and searchable online tool that consolidates and organizes resources, best practices, and lessons learned from previous small satellite missions sponsored by NASA, other government agencies, and academia. This free, publicly available tool is available to the entire SmallSat Community. The SSRI Knowledge Base provides vetted, high-quality sources of information on elements that are key to successful small satellite missions. These resources include SSRI working group generated documents and presentations in addition to existing guides, publications, standards, software tools, websites, and books. The Knowledge Base is fully searchable, offers downloadable content when possible, and otherwise links to or references content directly from within the tool. This presentation and paper will discuss the motivation for the SSRI Knowledge Base, review educational use cases, and outline plans for further development. The SSRI is a collaborative activity with broad participation from civil, U.S. Department of Defense, and both national and international commercial space systems providers and stakeholders. NASA’s Small Spacecraft Systems Virtual Institute (S3VI) funds the SSRI Knowledge Base. The S3VI is jointly sponsored by NASA’s Space Technology Mission Directorate and Science Mission Directorate

Detection of Near-IR CO Absorption Bands in R Coronae Borealis Stars

R Coronae Borealis (RCB) stars are hydrogen-deficient, carbon-rich pulsating post-AGB stars that experience massive irregular declines in brightness caused by circumstellar dust formation. The mechanism of dust formation around RCB stars is not well understood. It has been proposed that CO molecules play an important role in cooling the circumstellar gas so that dust may form. We report on a survey for CO in a sample of RCB stars. We obtained H- and K-band spectra including the first and second overtone CO bands for eight RCB stars, the RCB-like star, DY Per and the final-helium-flash star, FG Sge. The first and second overtone CO bands were detected in the cooler (T(eff)<6000 K) RCB stars, Z Umi, ES Aql, SV Sge and DY Per. The bands are not present in the warmer (T(eff)>6000 K) RCB stars, R CrB, RY Sgr, SU Tau, XX Cam. In addition, first overtone bands are seen in FG Sge, a final-helium-flash star that is in an RCB-like phase at present. Effective temperatures of the eight RCB stars range from 4000 to 7250 K. The observed photospheric CO absorption bands were compared to line-blanketed model spectra of RCB stars. As predicted by the models, the CO bands are strongest in the coolest RCB stars and not present in the warmest. No correlation was found between the presence or strength of the CO bands and dust formation activity in the stars.Comment: 13 oages, 3 figures, AJ in pres

Visible and Near-Infrared Spectrophotometry of the Deep Impact Ejecta of Comet 9P/Tempel 1

We have obtained optical spectrophotometry of the evolution of comet 9P/Tempel 1 after the impact of the Deep Impact probe, using the Supernova Integral Field Spectrograph (SNIFS) at the UH 2.2m telescope, as well as simultaneous optical and infrared spectra using the Lick Visible-to-Near-Infrared Imaging Spectrograph (VNIRIS) spectrograph. The spatial distribution and temporal evolution of the "violet band" CN (0-0) emission and of the 630 nm [OI] emission was studied. We found that CN emission centered on the nucleus increased in the two hours after impact, but that this CN emission was delayed compared to the light curve of dust-scattered sunlight. The CN emission also expanded faster than the cloud of scattering dust. The emission of [OI] at 630 nm rose similarly to the scattered light, but then remained nearly constant for several hours after impact. On the day following the impact, both CN and [OI] emission concentrated on the comet nucleus had returned nearly to pre-impact levels. We have also searched for differences in the scattering properties of the dust ejected by the impact compared to the dust released under normal conditions. Compared to the pre-impact state of the comet, we find evidence that the color of the comet was slightly bluer during the post-impact rise in brightness. Long after the impact, in the following nights, the comet colors returned to their pre-impact values. This can be explained by postulating a change to a smaller particle size distribution in the ejecta cloud, in agreement with the findings from mid-infrared observatons, or by postulating a large fraction of clean ice particles, or by a combination of these two.Comment: 28 pages of text and 8 figures. Paper is accepted for publication in Icaru

Variability of Disk Emission in Pre-Main Sequence and Related Stars. I. HD 31648 and HD 163296 - Isolated Herbig Ae Stars Driving Herbig-Haro Flows

Infrared photometry and spectroscopy covering a time span of a quarter century are presented for HD 31648 (MWC 480) and HD 163296 (MWC 275). Both are isolated Herbig Ae stars that exhibit signs of active accretion, including driving bipolar flows with embedded Herbig-Haro (HH) objects. HD 163296 was found to be relatively quiescent photometrically in its inner disk region, with the exception of a major increase in emitted flux in a broad wavelength region centered near 3 microns in 2002. In contrast, HD 31648 has exhibited sporadic changes in the entire 3-13 micron region throughout this span of time. In both stars the changes in the 1-5 micron flux indicate structural changes in the region of the disk near the dust sublimation zone, possibly causing its distance from the star to vary with time. Repeated thermal cycling through this region will result in the preferential survival of large grains, and an increase in the degree of crystallinity. The variability observed in these objects has important consequences for the interpretation of other types of observations. For example, source variability will compromise models based on interferometry measurements unless the interferometry observations are accompanied by nearly-simultaneous photometric data.Comment: 55 pages, 18 figures, 2 tables, Accepted by Ap

Early Infrared Spectral Development of V1187 Scorpii (Nova Scorpii 2004 No. 2)

We report on an unprecedented infrared time series of spectra of V1187 Sco, a very fast ONeMg nova. The observations covered a 56 day period (2004 August 6-September 30) starting 2 days after the nova's peak brightness. Time evolution of the spectra revealed changing line strengths and profiles on timescales of less than a day to weeks as the nova evolved from early postmaximum to early coronal phases. When our ground-based optical and Spitzer Space Telescope data were combined, the wavelength coverage of 0.38-36 μm allowed an accurate spectral energy distribution to be derived when it was about 6 weeks after outburst. Developing double structure in the He I lines showed them changing from narrow to broad in only a few days. Using the O I lines in combination with the optical spectra, we derived a reddening of E(B - V) = 1.56 ± 0.08 and a distance of 4.9 ± 0.5 kpc. Modeling of the ejected material strongly suggested that it was geometrically thick with ΔR/R = 0.8-0.9 (more of a wind than a shell) and a low filling factor of order a few percent. The line shapes were consistent with a cylindrical jet, bipolar, or spherical Hubble flow expansion with a maximum speed of about -3000 km s-1. The central peak appeared to be more associated with the spherical component, while the two peaks (especially in Hβ) suggested a ring with either a lower velocity component or with its axis inclined to the line of sight

SARS-CoV-2 lineage B.1.1.7 is associated with greater disease severity among hospitalised women but not men: multicentre cohort study.

BACKGROUND: SARS-CoV-2 lineage B.1.1.7 has been associated with an increased rate of transmission and disease severity among subjects testing positive in the community. Its impact on hospitalised patients is less well documented. METHODS: We collected viral sequences and clinical data of patients admitted with SARS-CoV-2 and hospital-onset COVID-19 infections (HOCIs), sampled 16 November 2020 to 10 January 2021, from eight hospitals participating in the COG-UK-HOCI study. Associations between the variant and the outcomes of all-cause mortality and intensive therapy unit (ITU) admission were evaluated using mixed effects Cox models adjusted by age, sex, comorbidities, care home residence, pregnancy and ethnicity. FINDINGS: Sequences were obtained from 2341 inpatients (HOCI cases=786) and analysis of clinical outcomes was carried out in 2147 inpatients with all data available. The HR for mortality of B.1.1.7 compared with other lineages was 1.01 (95% CI 0.79 to 1.28, p=0.94) and for ITU admission was 1.01 (95% CI 0.75 to 1.37, p=0.96). Analysis of sex-specific effects of B.1.1.7 identified increased risk of mortality (HR 1.30, 95% CI 0.95 to 1.78, p=0.096) and ITU admission (HR 1.82, 95% CI 1.15 to 2.90, p=0.011) in females infected with the variant but not males (mortality HR 0.82, 95% CI 0.61 to 1.10, p=0.177; ITU HR 0.74, 95% CI 0.52 to 1.04, p=0.086). INTERPRETATION: In common with smaller studies of patients hospitalised with SARS-CoV-2, we did not find an overall increase in mortality or ITU admission associated with B.1.1.7 compared with other lineages. However, women with B.1.1.7 may be at an increased risk of admission to intensive care and at modestly increased risk of mortality.This report was produced by members of the COG-UK-HOCI Variant substudy consortium. COG-UK-HOCI is part of COG-UK. COG-UK is supported by funding from the Medical Research Council (MRC) part of UK Research & Innovation (UKRI), the National Institute of Health Research (NIHR) and Genome Research Limited, operating as the Wellcome Sanger Institute

Polygenic prediction of educational attainment within and between families from genome-wide association analyses in 3 million individuals

We conduct a genome-wide association study (GWAS) of educational attainment (EA) in a sample of ~3 million individuals and identify 3,952 approximately uncorrelated genome-wide-significant single-nucleotide polymorphisms (SNPs). A genome-wide polygenic predictor, or polygenic index (PGI), explains 12-16% of EA variance and contributes to risk prediction for ten diseases. Direct effects (i.e., controlling for parental PGIs) explain roughly half the PGI's magnitude of association with EA and other phenotypes. The correlation between mate-pair PGIs is far too large to be consistent with phenotypic assortment alone, implying additional assortment on PGI-associated factors. In an additional GWAS of dominance deviations from the additive model, we identify no genome-wide-significant SNPs, and a separate X-chromosome additive GWAS identifies 57