Geoscience Laser Altimetry System (GLAS) Loop Heat Pipe Anomaly and On Orbit Testing

The Geoscience Laser Altimetry System (GLAS) is the sole instrument on the ICESat Satellite. On day 230 of 2003, the GLAS Component Loop Heat Pipe (CLHP) entered a slow circulation mode that resulted in the main electronics box reaching its hot safing temperature, after which the entire instrument was turned off. The CLHP had a propylene working fluid and was actively temperature controlled via a heater on the compensation chamber. The slow circulation mode happened right after a planned propulsive yaw maneuver with the spacecraft. It took several days to recover the CLHP and ensure that it was still operational. The recovery occurred after the entire instrument was cooled to survival temperatures and the CLHP compensation chamber cycled on a survival heater. There are several theories as to why this slow circulation mode exhibited itself, including: accumulation of Non-Condensible Gas (NCG), the secondary wick being under designed or improperly implemented, or an expanded (post-launch) leak across the primary wick. Each of these is discussed in turn, and the secondary wick performance is identified as the most likely source of the anomalous behavior. After the anomaly, the CLHP was controlled to colder temperatures to improve its performance (as the surface tension increases with lower temperature, as does the volume of liquid in the compensation chamber) and only precursor pulses occurred later in the mission. After GLAS s last laser failed, in late 2009, a decision was made to conduct engineering tests of both LHPs to try and duplicate this flight anomaly. The engineering tests consisted of control setpoint changes, sink changes, and one similar propulsive Yaw maneuver. The only test that showed any similar anomaly precursors on the CLHP was the propulsive maneuver followed by a setpoint increase. The ICESat Satellite was placed in a decaying orbit and ended its mission on August 30, 2010 in Barents Sea

Performance of the GLAS Space Lidar Receiver Through Its Seven-Year Space Mission

NASA s Ice, Cloud, and land Elevation Satellite (ICESat) mission [1,2] carrying the Geoscience Laser Altimeter System (GLAS) Instrument, was launched on January 12, 2003. The three lasers on ICESat have made a total of 1.98 billion laser shot measurements of the Earth s surface and atmosphere during its 17 science data collection campaigns over its seven year operating lifetime. ICESat completed its science mission after the last laser stopped operating in October 2009. The spacecraft was de-orbited on August 30, 2010. The GLAS instrument carried 3 diode-pumped Q-switched Nd:YAG lasers, which emitted 6-nsec wide pulses at 1064 and 532 nm at a 40-Hz rate. There are three lidar receiver channels, a 1064 nm surface altimetry channel, a 1064 nm cloud backscattering lidar channel, and a 532 nm cloud and aerosol backscattering lidar channel. The altimetry and cloud backscatter channels used Si avalanche photodiode (APD) operated in analog mode as in the Mars Global Surveyor s Mars Orbital Laser Altimeter [3,4]. GLAS also utilized a number of new technologies and techniques for space lidar, including passively Q-switched diode-pumped Nd:YAG lasers, a 1-m diameter telescope, a temperature tuned etalon optical bandpass filter, Si APD single photon counting detectors, 1 Gsample/sec waveform digitizers, ultra stable clock oscillators, and digital signal processing and detection algorithms [5]. A global position system (GPS) receiver was used to provide the spacecraft position and epoch times. The ICESat mission provided a unique opportunity to monitor the lidar component performance in the space environment over a multi-year time period. We performed a number of engineering tests periodically to monitor the lidar receiver performance, including receiver sensitivity, timing precision, detector dark noise, etc. A series of engineering tests were also performed after the end of the science mission to evaluate the performance of the spare detector, oscillator, waveform digitizer, and GPS receiver. An experiment was conducted which pointed GLAS to Venus to test the receiver sensitivity to star light and to verify GLAS bore sight with respect to the spacecraft coordinate system. These tests provided unique data to assess the degradation and the rate of change of these key lidar components due to space radiation and aging. They also helped to validate new techniques to operate and calibrate future space lidars

The Algorithm Theoretical Basis Document for Level 1A Processing

The first process of the Geoscience Laser Altimeter System (GLAS) Science Algorithm Software converts the Level 0 data into the Level 1A Data Products. The Level 1A Data Products are the time ordered instrument data converted from counts to engineering units. This document defines the equations that convert the raw instrument data into engineering units. Required scale factors, bias values, and coefficients are defined in this document. Additionally, required quality assurance and browse products are defined in this document

On Orbit Receiver Performance Assessment of the Geoscience Laser Altimeter System (GLAS) on ICESAT

The GLAS instrument on the NASA's ICESat mission has provided over a billion measurements of the Earth surface elevation and atmosphere backscattering at both 532 and 1064-nm wavelengths. The receiver performance has stayed nearly unchanged since ICESat launch in January 2003. The altimeter receiver has achieved a less than 3-cm ranging accuracy when excluding the effects of the laser beam pointing angle determination uncertainties. The receiver can also detect surface echoes through clouds of one-way transmission as low as 5%. The 532-nm atmosphere backscattering receiver can measure aerosol and clouds with cross section as low as 1e-7/m.sr with a 1 second integration time and molecular backscattering from upper atmosphere with a 60 second integration time. The 1064-nm atmosphere backscattering receiver can measure aerosol and clouds with a cross section as low as 4e-6/m.sr. This paper gives a detailed assessment of the GLAS receiver performance based on the in-orbit calibration tests

Educator Self-Care, Resiliency, and Inclusion

Acosta, J., Chandra, A., & Madrigano, J. (2017) stated that “Resilience is defined as the capacity of any dynamic system to anticipate and adapt successfully to difficulties. Individual resilience is the process of, capacity for, or outcome of adapting well in the face of adversity, trauma, tragedy, threats, or significant sources of stress.” The Seven streams of resilient behavior – community, competence, connections, commitment, communication, coordination, and consideration – act as a whole system response, as a practical theory that has the capacity to adapt and mold to changing data and shifting circumstances in the face of new technology according to Horne, J. F., III, & Orr, J. E, 1998. Resilience is a combination of social competence and pro-social values, optimism, purpose, an attachment to family, to school and learning, problem-solving skills, an effective coping style, and a positive self-image. Kintsugi is an ancient Japanese art meaning ‘to join with gold.’ Kintsugi consists of assembling “broken pieces of an accidentally-smashed pot” (The Book of Life, 2018). Kintsugi celebrates imperfection. The broken pieces of the pot are glued together with “lacquer inflected with a very luxuriant gold powder” (The Book of Life, 2018). The visible fractures are adorned with gold rather than hidden. Symbolically, the golden cracks represent the worth of the bowl because of its imperfections rather than in spite of them. The bowl is like a human, cracked by the contingency of life. The gold endows the pot with unassailable beauty, uniqueness, and strength. There is a lesson for embracing failures and experiences that crack our spirit. How do we turn those life cracks into gold? This relates back to our idea of building resilient educators so that they can serve children in inclusive, quality learning environments

SUBJECTIVE SOCIAL STATUS MODERATES BACK PAIN AND MENTAL HEALTH: A LONGITUDINAL ANALYSIS OF OLDER MEN

Abstract Objectives. This study tested the longitudinal relationship between back pain and mental health and examined the moderating role of subjective social status (SSS). Method. Community-dwelling older men from the MrOS Study provided four study visits of data collected between 2000-2016 (15,975 observations nested within 5,979 participants). Back pain frequency and severity were assessed at visits 1-4. General mental health was measured at each visit by the 12-item Short Form Survey Mental Component Score (SF-12 MCS; higher scores representing better mental health). National and community SSS were assessed at visits 1 and 3 with the MacArthur Scale. Growth curve models tested longitudinal within-person change associations after accounting for the repeated measures within each person. Age was used as the primary time variable. Results. At baseline, those with higher back pain-frequency/severity reported lower SF-12 MCS. After accounting for this between-person difference, there were bidirectional within-person associations between back pain frequency/severity and SF-12 MCS. On follow-up visits when back pain frequency/severity increased from baseline, participants reported lower SF-12 MCS (p<.001). On follow-up visits when SF-12 MCS decreased from baseline, participants also reported higher back pain frequency/severity (p<.001). Higher national and community SSS at baseline and having increases or consistently higher SSS over time attenuated the negative relationships between back pain frequency/severity and SF-12 MCS. Results were consistent after controlling for an extensive list of baseline health covariates and pain medications. Discussion. These findings highlight how self-perceived social status may buffer the relationship between greater back pain frequency/severity and lower mental health

Subjective social status moderates back pain and mental health in older men

ObjectivesBack pain and poor mental health are interrelated issues in older men. Evidence suggests that socioeconomic status moderates this relationship, but less is known about the role of subjective social status (SSS). This study examined if the association between back pain and mental health is moderated by SSS.MethodWe used a sample of community-dwelling older men (≥65 years) from the Osteoporotic Fractures in Men Study (N = 5994). Participants self-reported their back pain severity and frequency over the past 12 months. SSS was assessed with the MacArthur Scale of SSS. Mental health was assessed with the SF-12 Mental Component Summary (MCS).ResultsSevere back pain was associated with lower SF-12 MCS scores (p = .03). Back pain frequency was not associated with SF-12 MCS scores. SSS moderated the back pain and mental health relationship. Among men with higher national or community SSS, the association between back pain severity and SF-12 MCS scores was not significant. However, among men with lower national or community SSS, more severe back pain was associated with lower SF-12 MCS scores (p's < .001). Among those with lower national or community SSS, greater back pain frequency was also associated with lower SF-12 MCS scores (p's < .05).ConclusionWhere one ranks oneself within their nation or community matters for the back pain and mental health relationship. Higher SSS may be a psychosocial resource that buffers the negative associations of severe and frequent back pain on mental health in older men