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We present here the current state of a collection of promising ultraviolet technologies in preparation for the Habitable Worlds Observatory. Working with experts representing a significant number of groups working in the ultraviolet, we summarize some of the leading science drivers, present an argument for a 100 nm blue wavelength cutoff, and gather current state of the art of UV technologies. We present the state of the art of contamination control, a crucial piece of the UV instrument plan. We explore next steps with individual technologies, as well as present paths forward with systems level testing and development.

We observe quantum beats in the nanosecond-scale photoluminescence decay of rubrene single crystals after photoexcitation with short laser pulses in a magnetic field of 0.1 to 0.3 T. The relative amplitude of the quantum beats is of the order of 5\%. Their frequency is $1.3$ GHz when the magnetic field is oriented parallel to the two-fold rotation axis of the rubrene molecules and decreases to $0.6$ GHz when the magnetic field is rotated to the crystal's molecular stacking direction. The amplitude of the quantum beats decays alongside the non-oscillatory photoluminescence background, which at low excitation densities has an exponential decay time of $ 4.0 \pm 0.2$~ns. We interpret this as the effective lifetime of a multiexciton state that originates from singlet-fission and can undergo geminate recombination back to the singlet state., Comment: 4 pages, 4 figures

FIREBall-2 is a stratospheric balloon-borne 1-m telescope coupled to a UV multi-object slit spectrograph designed to map the faint UV emission surrounding z~0.7 galaxies and quasars through their Lyman-alpha line emission. This spectro-imager had its first launch on September 22nd 2018 out of Ft. Sumner, NM, USA. Because the balloon was punctured, the flight was abruptly interrupted. Instead of the nominal 8 hours above 32 km altitude, the instrument could only perform science acquisition for 45 minutes at this altitude. In addition, the shape of the deflated balloon, combined with a full Moon, revealed a severe off-axis scattered light path, directly into the UV science detector and about 100 times larger than expected. In preparation for the next flight, and in addition to describing FIREBall-2's upgrade, this paper discusses the exposure time calculator (ETC) that has been designed to analyze the instrument's optimal performance (explore the instrument's limitations and subtle trade-offs).

Modern grating manufacturing techniques suffer from inherent issues that limit their peak efficiencies. The anisotropic etching of silicon facilitates the creation of custom gratings that have sharp and atomically smooth facets, directly addressing these issues. We describe work to fabricate and characterize etched silicon echelles optimized for the far ultraviolet (FUV; 90 - 180 nm) bandpass. We fabricate two echelles that have similar parameters to the mechanically ruled grating flown on the CHESS sounding rocket. We demonstrate a 42% increase in peak order efficiency and an 83% decrease in interorder scatter using these gratings. We also present analysis on where the remaining efficiency resides. These demonstrated FUV echelle improvements benefit the faint source sensitivity and high-resolution performance of future UV observatories., Comment: 21 pages, 13 figures, Accepted into Applied Optics

Photon counting detector systems on sounding rocket payloads often require interfacing asynchronous outputs with a synchronously clocked telemetry (TM) stream. Though this can be handled with an on-board computer, there are several low cost alternatives including custom hardware, microcontrollers and field-programmable gate arrays (FPGAs). This paper outlines how a TM interface (TMIF) for detectors on a sounding rocket with asynchronous parallel digital output can be implemented using low cost FPGAs and minimal custom hardware. Low power consumption and high speed FPGAs are available as commercial off-the-shelf (COTS) products and can be used to develop the main component of the TMIF. Then, only a small amount of additional hardware is required for signal buffering and level translating. This paper also discusses how this system can be tested with a simulated TM chain in the small laboratory setting using FPGAs and COTS specialized data acquisition products., Comment: 16 pages, 11 pages (also published as a 2015 SPIE conference proceeding)

Community colleges enroll a diverse set of students who often face challenges meeting their basic needs. This report describes the potential benefits and costs of one low-cost and relatively light-touch tool that colleges might use to increase students' access to basic needs assistance. The authors focus on the Findhelp platform, which is modeled as a "social care network" that connects students through an online platform to services that provide help. Findhelp is a website that lists local resources and services, and it is available to anyone affiliated with an institution partnering with the platform. There is little research on Findhelp and similar light-touch resources, so this research documents how the resource was implemented at four community colleges in North Carolina, its implementation costs, and its impacts on student success following implementation. The authors use information from interviews with the campus staff who implemented the platform, administrative student-level data from the North Carolina Community College System on student persistence and credits attempted and completed, and data from Findhelp on how much individual students interacted with the platform. Overall, Findhelp usage rates were low, though usage varied across the participating colleges. Campus staff were enthusiastic about the potential of the platform, and there is some evidence that student success increased when the platform was implemented. In addition, the platform was relatively low-cost to implement compared with other more-intensive approaches for supporting students' basic needs.

Stackable credential programs--that is, programs that facilitate students' ability to earn multiple postsecondary certificates or degrees--have been a priority for Ohio, which has a long history of legislation, state and regional initiatives, and institution-led efforts to build more-effective pathways to address the needs of employers and students. To assess progress and inform ongoing efforts to scale stackable credentials, the Ohio Department of Higher Education and the RAND Corporation established a research partnership. In this report, RAND researchers examine students who earned postsecondary certificates in health care, manufacturing and engineering technology (MET), or information technology (IT) fields at Ohio institutions between the 2004-2005 and 2012-2013 academic years and went on to earn (or stack) additional educational credentials. The authors descriptively examine the completion of credentials over time, the types of students who are earning certificates and going on to stack credentials, the subfields and levels of credentials earned, the types of institutions students earned credentials from, and the credit accumulation and terms of enrollment for students earning different types of credentials. The findings indicate increased numbers of students earning certificates and stacking credentials in Ohio. Certificate-earners were diverse, but rates of stacking were lower for Black students and adult learners (i.e., ages 25 and older). Most of the students who stacked credentials had earned a degree within four years, and most stacked within the same field.

This paper presents Rocket Experiment (REX) that was part of a dual payload rocket campaign for NASA's sounding rocket Black Brant IX with water recovery technology. This mission was a suborbital sounding rocket flight that was launched and recovered on April 4, 2018 and targeted the Vela supernova remnant. The purpose of REX was to classify the Technology Readiness Level of onboard devices designed for space applications. The devices were two wide-field X-ray telescopes consisting of a combination of Lobster-Eye (LE) optics with an uncooled Timepix detector (256 x 256 px @ 55 um), and additional sensors. The first telescope uses a two-dimensional combination of LE modules with a focal length of 1 m and a Field of View (FOV) of 1.0 x 1.2 deg and operates in the energy range of 3 - 60 keV. The second telescope was a one-dimensional LE with a focal length of 250 mm and a FOV of 2.7 x 8.0 deg for the energy range 3 - 40 keV. The X-ray telescopes were supplemented by a camera in the visible spectrum with 1,280 x 1,024 px resolution, which was used to obtain images of the observed sources and to verify the resulting pointing of the rocket carrier. Other devices also include infrared array sensors and inertial measurement units tested for future small satellite missions. The data handler and communication system were built using the Robot Operating System, and both the system and the electronics were deployed and operated in flight. The hardware was successfully recovered after the launch and the data were extracted., Comment: Submitted to Acta Astronautica

Surface-relief gratings fabricated through nanoimprint lithography (NIL) are prone to topographic distortion induced by resist shrinkage. Characterizing the impact of this effect on blazed diffraction efficiency is particularly important for applications in astrophysical spectroscopy at soft x-ray wavelengths ($\lambda \approx 0.5 - 5$~nm) that call for the mass-production of large-area grating replicas with sub-micron, sawtooth surface-relief profiles. A variant of NIL that lends itself well for this task is substrate-conformal imprint lithography (SCIL), which uses a flexible, composite stamp formed from a rigid master template to imprint nanoscale features in an inorganic resist that cures thermodynamically through a silica sol-gel process. While SCIL enables the production of several hundred imprints before stamp degradation and avoids many of the detriments associated with large-area imprinting in NIL, the sol-gel resist suffers shrinkage dependent on the post-imprint cure temperature. Through atomic force microscopy and diffraction-efficiency testing at beamline 6.3.2 of the Advanced Light Source, the impact of this effect on blaze response is constrained for a $\sim$160-nm-period grating replica cured at 90$^{\circ}$C. Results demonstrate a $\sim$2$^{\circ}$ reduction in blaze angle relative to the master grating, which was fabricated by anisotropic wet etching in $\langle 311 \rangle$-oriented silicon to yield a facet angle close to 30$^{\circ}$., Comment: 17 pages, 11 figures

Official counts of COVID-19 deaths have been criticized for potentially including people who did not die of COVID-19 but merely died with COVID-19. I address that critique by fitting a generalized additive model to weekly counts of all deaths registered in England and Wales during the 2010s. The model produces baseline rates of death registrations expected without the COVID-19 pandemic, and comparing those baselines to recent counts of registered deaths exposes the emergence of excess deaths late in March 2020. By April's end, England and Wales registered 45,300 $\pm$ 3200 excess deaths of adults aged 45+. Through 22 May, the last day of available all-deaths data, 56,600 $\pm$ 4400 were registered (about 53% of which were of men). Both the ONS's corresponding count of 43,205 death certificates which mention COVID-19, and the Department of Health and Social Care's count of 33,671 deaths, are appreciably less, implying that their counting methods have underestimated, not overestimated, the pandemic's true death toll. If underreporting rates have held steady during May, about 59,000 direct and indirect COVID-19 deaths might have been registered through the end of May but not yet publicly reported in full., Comment: 27 A4 pages, 4 tables, 14 figures, 2 appendices

Future observatories utilizing reflection grating spectrometers for extreme ultraviolet (EUV) and soft X-ray (SXR) spectroscopy require high-fidelity gratings with both blazed groove facets and custom groove layouts that are often fanned or feature a slight curvature. While fabrication procedures centering on wet anisotropic etching in monocrystalline silicon produce highly efficient blazed gratings, the precision of a nonparallel groove layout is limited by the cubic structure of the silicon crystal. This motivates the pursuit of alternative techniques to grating manufacture, namely thermally activated selective topography equilibration (TASTE), which uses gray-scale electron-beam lithography to pattern multilevel structures in resist followed by an optimized polymer thermal reflow to smooth the 3D patterns into continuous surface relief profiles. Using TASTE, a mold for a reflection grating with a periodicity of 400 nm and grooves resembling an asymmetric sawtooth was patterned in 130 nm thick poly(methyl methacrylate) resist on a silicon substrate over a 50 mm by 7.5 mm area. This structure was coated with 15 nm of gold by electron-beam physical vapor deposition using titanium as an adhesion layer and then tested for EUV and SXR diffraction efficiency at beamline 6.3.2 of the Advanced Light Source synchrotron facility. Results demonstrate a quasi-blaze response characteristic of a 27 degree blaze angle with groove facets smooth to 1.5 nm rms. Absolute peak-order efficiency ranges from 75% to 25%, while total relative efficiency measures gap90% across the measured bandpass of 15.5 nm > lambda > 1.55 nm., Comment: 19 pages, 16 figures

Most students finish high school with low levels of financial knowledge, yet they are months away from important decisions about how to finance college. Students may not know about family finances, even though parental income is a key determinant of financial aid for college. This study measures the financial knowledge of high school students by comparing survey answers to actual measures of parental income from financial aid applications in a statewide sample. We find that students can accurately state parental income 24% of the time, within $15,000. Overreporting of parental income is much more common than underreporting. We explore potential causes and consequences of misreporting, and implications for research using self-reported income.

Instead of enrolling for four or more years to get a bachelor's degree, what if individuals could work their way toward a degree gradually? First, they would attend college or a trade school for six months or a year and earn a certificate that prepares them for an entry-level job in various fields. Then, they would pursue additional knowledge and skills at the time they need them to advance their careers, reenrolling in college to continue progress toward a second certificate or degree. This might allow these individuals to invest their time and tuition dollars more strategically, and they might come away with training that better fits their needs. This approach to education and training is often referred to as "stackable credentials." Stackable credentials are most common in fields that offer many "middle skill" jobs--those that require some postsecondary education and training below the bachelor's degree level--such as health care and information technology. Ohio has been a leader in scaling stackable credential programs. It established statewide agreements that require credits to be awarded for certain blocks of coursework that previously were not eligible for credit, and it increased the funding allocated to certificate programs. Have institutions changed the programs that they offer? Are students stacking credentials, and, when they do, are they seeing an increase in earnings? Researchers at the RAND Corporation and the Ohio Department of Higher Education (ODHE) established a multiyear partnership to answer these questions and others. To find the answers, the team examined the state's stackable credential offerings and student outcomes in three fields: health care, manufacturing and engineering technology (MET), and information technology (IT). This brief describes work in the reports "Stacking Educational Credentials in Ohio: Pathways Through Postsecondary Education in Health Care, Manufacturing and Engineering Technology, and Information Technology" (ED613709); "Making Improvements to Stackable Credential Pipelines: A Toolkit on Using Data to Drive Improvement in Ohio Postsecondary Institutions" (ED613757); and "Stackable Credential Pipelines in Ohio: Evidence on Programs and Earnings Outcomes" (ED613593).

Almost every state offers some kind of college tuition assistance for students from low-income families who attend in-state colleges and universities. This aid is important: It can make all the difference as to whether students finish a degree program that can help pave their way to a well-paying job and meaningful career. In New Jersey, residents attending in-state colleges and universities can receive grants from the Tuition Aid Grant (TAG) program. Grants range from $1,000 to more than $12,000 per year that students can apply toward college costs and do not need to pay back. Students qualify based on a complicated formula that considers their family's income and assets, adjusting for age and the type of college they attend. While other state and federal aid programs have lost ground to tuition growth, TAG has maintained its status as the most generous program in the nation per undergraduate student. Focusing on eligibility thresholds is not a new idea, but RAND researchers combined hundreds of different thresholds to evaluate how aid effectiveness varied by family financial resources. The research team considered how TAG works differently across the state's many different higher education institutions: community colleges, public universities, and private nonprofit colleges. This brief summarizes some key findings, with details in the full report "Cutting the College Price TAG: The Effects of New Jersey's Tuition Aid Grant on College Persistence and Completion. Research Report. RR-A101-1" (ED612167).

RAND researchers studied more than 450,000 recipients of New Jersey's Tuition Aid Grant (TAG) -- the nation's most generous state-funded grant program per state resident college student -- to explore whether getting larger amounts of grant aid led to higher graduation rates for students at varying income levels and attending two-year, four-year, public, and private institutions. The data set covered school years 2012-2013 through 2019-2020 at 52 colleges and universities. Students received from $1,000 to $13,000 per year in TAG awards, plus $600 to $6,000 per year in federal Pell Grant aid. Grants help students cover tuition and living expenses and do not need to be paid back. On average, TAG aid increased the rate of on-time bachelor's degree completion at public universities, the sector where TAG has the most recipients and covers the largest percentage of tuition costs. An additional $1,000 in aid over four years led to a 2.6 percentage point increase in the graduation rate from a sample average graduation rate of 35 percent, a significant increase and higher than the average effect found in prior studies of other aid programs. In community colleges and at private colleges and universities, the effect of TAG for its lowest-income recipients on four-year graduation outcomes was positive and marginally statistically significant.

Stackable credential initiatives aim to build education and training pipelines in applied fields that allow individuals to earn educational certificates or other industry-recognized credentials and then build on these short-term credentials to earn additional certificates and degrees throughout their careers. Stackable credentials have the potential to provide more flexible education and training options for individuals and align better with employer needs. Stackable credentials are a priority for Ohio and a national trend in postsecondary institutions, yet little research has been conducted on whether institutions are scaling stackable programs, how students are stacking credentials, and whether these programs benefit individuals and employers. In this report, the authors examine Ohio's stackable credential pipelines in three fields--health care, manufacturing and engineering technology, and information technology--during the period between 2005 and 2019. They explore two areas: (1) growth in short-term education programs offered by Ohio public institutions and the degree to which programs incorporated features that characterize stackable credentials; and (2) earnings outcomes for certificate-earning students who went on to stack postsecondary education credentials. [For the technical appendix to this report, see ED613594.]

Experts from the RAND Corporation prepared this independent report on New Jersey's Tuition Aid Grant (TAG) program for low-income college students. TAG is the nation's most generous state-funded financial aid program on a per-resident-undergraduate basis. Currently, TAG distributes around $475 million in grants per year, and an award covers about 40 percent of the average recipient's tuition and fees. Recent evidence shows positive impacts of the program on graduation. Leaders in New Jersey are further evaluating TAG to explore how the program design has evolved and how it might be improved. The authors used new data sources to build actionable evidence on each of the issues put before a legislatively mandated TAG Study Commission. These issues include TAG recipients' graduation rates, the history of program design choices and funding, alternative eligibility calculations, and alignment with federal methods. The authors drew on conversations with the Higher Education Student Assistance Authority and the commission, analysis of student-level data from New Jersey, analysis of institution-level data from the College Scorecard, and context from other states and broader research on college affordability. The authors evaluated policy options discussed by commission members and put forth some added considerations that could be important for the state and for other states with need-based aid programs.

Future soft X-ray (10 - 50 Angstrom) spectroscopy missions require higher effective areas and resolutions to perform critical science that cannot be done by instruments on current missions. An X-ray grating spectrometer employing off-plane reflection gratings would be capable of meeting these performance criteria. Off-plane gratings with blazed groove facets operated in the Littrow mounting can be used to achieve excellent throughput into orders achieving high resolutions. We have fabricated two off-plane gratings with blazed groove profiles via a technique which uses commonly available microfabrication processes, is easily scaled for mass production, and yields gratings customized for a given mission architecture. Both fabricated gratings were tested in the Littrow mounting at the Max-Planck-Institute for extraterrestrial Physics PANTER X-ray test facility to assess their performance. The line spread functions of diffracted orders were measured, and a maximum resolution of 800 $\pm$ 20 is reported. In addition, we also observe evidence of a `blaze' effect from measurements of relative efficiencies of the diffracted orders., Comment: 25 pages including references

An X-ray spectrograph consisting of radially ruled off-plane reflection gratings and silicon pore optics was tested at the Max Planck Institute for extraterrestrial Physics PANTER X-ray test facility. The silicon pore optic (SPO) stack used is a test module for the Arcus small explorer mission, which will also feature aligned off-plane reflection gratings. This test is the first time two off-plane gratings were actively aligned to each other and with a SPO to produce an overlapped spectrum. The gratings were aligned using an active alignment module which allows for the independent manipulation of subsequent gratings to a reference grating in three degrees of freedom using picomotor actuators which are controllable external to the test chamber. We report the line spread functions of the spectrograph and the actively aligned gratings, and plans for future development., Comment: Draft Version March 19, 2015

Making college accessible to all includes making it affordable to lower-income families. A growing policy strategy at the state level is to provide individual students with need-based financial aid to offset tuition and living expenses. This strategy inherently presents challenges in choosing which income levels are eligible to receive aid, identifying the eligible population, and delivering aid at a time and in an amount that will meaningfully support college attainment. In partnership with the state of Wisconsin, RAND Corporation researchers created and analyzed a new database connecting state grant aid applications to the educational attainment of applicants. This report is a case-based effort to shed light on how well state aid policies are doing at closing attainment gaps between students from low- and higher-income backgrounds. It focuses on the successes, challenges, and opportunities for the state of Wisconsin and its flagship aid program, the Wisconsin Grant. This report examines three areas: the "design" of effective aid policies and processes, "program implementation" under time and budget constraints, and the "building of evidence" on aid program effectiveness. The findings related to the Wisconsin case can inform the state on how to build on successes and mediate challenges related to state student aid going forward. The findings also offer insight to other states wanting to better design, implement, and build evidence for their state student aid programs.

State policies to promote postsecondary education historically have been devoted to funding and operating public colleges and universities. Increasingly, states are funding direct aid to their residents to attend public and private colleges within state borders. The majority of state aid is targeted based on the student's family income. States are motivated to help their lowest-income residents graduate at higher rates, because degrees serve as pathways to long-term financial gain, career satisfaction, better health, lower rates of crime, and other positive outcomes. Yet, despite access to grant aid and open admissions to public colleges, students from lower-income backgrounds are far less likely than their higher-income peers to enroll in and graduate from college. What can state aid programs do to assure that more low-income students finish degrees? The RAND Corporation's Education and Labor division recently published a report that uses Wisconsin's state student aid policy as a case study to examine the design, implementation, and evidence base of state need-based aid. [This brief describes research documented in "Need-Based Financial Aid in Wisconsin: State Policy and Student Pathways. Research Report. RR-3057-GLHEC" (ED605976).]

With open admission policies, reasonable tuition rates, and convenient locations, community colleges are a good choice for many who want to improve their career outlooks or explore college to see whether a four-year program is for them. Yet, no matter their reason for entering, most students do not leave with a degree. For many years, federal and state governments have tried to increase college completion among low-income students through targeted, need-based financial aid. Although state budgets for financial aid have increased, state appropriations to support colleges and help keep tuition low have stagnated. To build evidence for state policy, RAND researchers examined the Wisconsin Grant program for technical college students. This study focused on students who applied for aid to attend one of the 16 technical colleges that make up the Wisconsin Technical College System (WTCS) and did so at any time during the 2010-2011 to 2014-2015 school years. The study sought to answer two questions: (1) Did Wisconsin Grant aid help increase graduation rates from technical colleges?; and (2) How might financial aid policy be adjusted to improve graduation for those who most need aid? Given the existence of federal aid programs, it is unclear whether the state should provide additional help to the poorest families or complement that aid with help to middle-income families. This study therefore investigated where Wisconsin Grants had their largest impact.

A dust grain in a plasma has a fluctuating electric charge, and past work concludes that spherical grains in a stationary, collisionless plasma have an essentially Gaussian charge probability distribution. This paper extends that work to flowing plasmas and arbitrarily large spheres, deriving analytic charge probability distributions up to normalizing constants. We find that these distributions also have good Gaussian approximations, with analytic expressions for their mean and variance., Comment: 10 pages & 6 figures. v3 corrects two typos in published version (missing slash added in denom. of eq. 66 and, on the same page, an order-of estimate's fixed to O(1/{\alpha}))

Although living organisms are affected by many interrelated and unidentified variables, this complexity does not automatically impose a fundamental limitation on statistical inference. Nor need one invoke such complexity as an explanation of the "Truth Wears Off" or "decline" effect; similar "decline" effects occur with far simpler systems studied in physics. Selective reporting and publication bias, and scientists' biases in favour of reporting eye-catching results (in general) or conforming to others' results (in physics) better explain this feature of the "Truth Wears Off" effect than Rabin's suggested limitation on statistical inference., Comment: 4 pages, no figures, 11 references. Commentary on Y. Rabin, Journal of Statistical Physics, 144, 213-216 (2011)

HaloSat is the first mission funded by NASA’s Astrophysics Division to use the CubeSat platform. Using three co-aligned silicon drift detectors, the HaloSat observatory measures soft (0.4 to 7 keV) x-ray emission from sources of diffuse emission such as the hot, gaseous halo of the Milky Way. We describe the design and construction of the science payload on HaloSat and the reasoning behind many of the choices. As a direct result of the design choices and adherence to best practices during construction, the HaloSat science payload continues to perform well after more than one year on-orbit.

Uncertainty in erosion rates as measured by different methods is discussed and quantified. The work focuses on case studies from components on the Hall Effect Rocket with Magnetic Shielding (HERMeS) Hall thruster, but the methods can be extended for many electric propulsion applications. The primary method used for evaluating erosion is non-contact profilometry of masked and exposed components. Accurate quantification of the erosion rates of components is critical to determining lifetime and is therefore critical to mission planning purposes.

Uncertainty in erosion rates as measured by different methods is discussed and quantified. The work focuses on case studies from components on the Hall Effect Rocket with Magnetic Shielding (HERMeS) Hall thruster, but the methods can be extended for many electric propulsion applications. The primary method used for evaluating erosion is non-contact profilometry of masked and exposed components. Accurate quantification of the erosion rates of components is critical to determining lifetime and is therefore critical to mission planning purposes.

The design of a new diagnostic to measure the net erosion of Hall thruster surfaces is presented. This diagnostic consists of a pair of optical noncontact profilometer pens mounted to a set of motion stages, which can interrogate the surface features of multiple components of interest including the hollow cathode assembly, magnet front pole covers, and discharge channel. By comparing scans of these surfaces to reference features, estimates of the component erosion rates can be acquired throughout long-duration lifetime tests without venting and removing the thruster from the vacuum facility for external profilometry. This work presents a detailed overview of the diagnostic design including the precision positioning system. In addition, preliminary data are shown which verify diagnostic operation and establish a baseline that will be used to track the erosion of the Hall Effect Rocket with Magnetic Shielding (HERMeS) Technology Demonstration Unit 3 (TDU-3) during an ongoing long-duration wear test.

A diagnostic has been designed and fabricated to verify the thrust vector requirement for the Advanced Electric Propulsion System (AEPS) Hall Effect Rocket with Magnetic Shielding (HERMeS) thruster. This diagnostic will be used to verify that the propulsion system thrust vector offset from the mounting surface normal vector does not exceed 1.5 degrees over the entire throttling range and over the course of 23,000 hours of thruster testing. The diagnostic will also not violate the thruster's required voltage standoff capability in the presence of carbon backsputter by being minimally intrusive and not significantly adding to the facility backsputtered rate. Based on these requirements, an appropriate diagnostic design was determined to comprise of an array of 23 Faraday probes swept through the plume in an arc 1m from the thruster to map the beam current density. The beam current density centroid of the plume is assumed to track the thrust vector within an acceptable level of uncertainty. Additionally, a reference system, including optical alignment to the mounting surface normal vector and tilt sensors, was devised to periodically calibrate the probe position and motion throughout the long duration wear test campaign. Initial measurements of the thruster plume have been acquired to demonstrate the diagnostics functionality, verify procedures, and assess any necessary improvements prior to implementation of the diagnostic during the AEPS Engineering Development Unit (EDU) long duration wear test. To illustrate the merits of differing approaches to thrust vector determination for different classes of electric propulsion thrusters, NASA's Evolutionary Xenon Thruster-Commercial (NEXT-C) thrust vector diagnostic design details and recent data are also discussed (Appendix A).

The Hall-Effect Rocket with Magnetic Shielding (HERMeS) thruster is being developed and tested at NASA GRC and NASA JPL through support of the Space Technology Mission Directorate (STMD) as primary propulsion for the Asteroid Redirect Robotic Mission (ARRM). This thruster is advancing the state-of-the-art of Hall-effect thrusters and is intended to serve as a precursor to higher power systems for human interplanetary exploration. A 2000-hour wear test has been initiated at NASA GRC with the HERMeS Technology Demonstration Unit One and three of four test segments have been completed totaling 728 h of operation. This is the first test of a NASA-designed magnetically shielded thruster to extend beyond 300 hr of continuous operation. Trends in performance, component wear, thermal design, plume properties, and back-sputtered deposition are discussed for two wear-test segments of 246 h and 360 h. The first incorporated graphite pole covers in an electrical configuration where cathode was electrically connected to thruster body. The second utilized traditional alumina pole covers with the thruster body floating. It was shown that the magnetic shielding in both configurations completely eliminated erosion of the boron nitride discharge channel but resulted in erosion of the inner pole cover. The volumetric erosion rate of the graphite pole covers was roughly 2/3 that of the alumina pole covers and the thruster exhibited slightly better performance. Buildup of back-sputtered carbon on the BN channel at a rate of roughly 1.5 μm/kh is shown to have negligible impact on the performance.