Naval Postgraduate School Petite Amateur Navy Satellite (PANSAT)

The Naval Postgraduate School\u27s (NPS) Space Systems Academic Group (SSAG) is designing and developing a small communications satellite. The objectives of PANSAT are three-fold. First, PANSAT will provide an ideal educational tool for the officer students at NPS supporting Space Systems Engineering and Space Systems Operations with hands-on hardware development. Secondly, the satellite will provide digital store-and-forward communications, or Packet Radio, for the amateur radio community. The third objective is to provide a low-cost, space-based platform for small experiments. PANSAT will be launched into Low Earth Orbit (LEO) for NPS coverage. The satellite weight is 150 lbs. Since there is no attitude control, dipole whip antennas will be used to provide isotropic ground coverage for communications. FM digital communications will be used with up-link and down-link on a single frequency in the proposed amateur band of 437.25 MHz. 25 kHz of bandwidth will be required. The expected life of the satellite is 1 1/2 to 2 years. The PANSAT design consists of the following: Communications Subsystem (COMM); Computer, or Data Processor & Sequencer (DP&S); Power Subsystem; Structure Subsystem; and Experiment Payload. The following is an overview of the project outlining initial design studies in the areas of the computer subsystem and structure subsystem and articulation on the specifications of the other subsystems

A Design Template for GAS Satellite Payloads

The Naval Postgraduate School has designed a small, low cost, general purpose satellite bus, ORION. An investigation of the structural requirements has been done for ORION as an extended Get Away Special (GAS) canister payload. The structure must be able to withstand the design limit load of 6.0 g\u27s acceleration in ± X and ± Y, and a limit load of 10.0 g\u27s in the ± Z. The structure must also have modal vibration greater than 35 Hz. A finite element analysis in linear bending considers an aluminum stiffened cylinder with two equipment plates and a top plate. Considerable weight reduction from the original design results. The structure configured for ORION may be helpful to other GAS payload users as a design template for similar satellites

Overview of the NPS Spacecraft Architecture and Technology Demonstration Satellite, NPSAT1

This paper describes the overall design of NPSAT1, a low-cost, technology demonstration satellite which hosts a number of experiments. The command and data handling (C&DH) subsystem is built on commercial, desktop PC architecture, and standards-based specifications. Combining PC hardware and a PC/104 interface bus with the robust Linux operating system software offers a means of addressing the uncertainty and difficulty of managing space systems software. NPSAT1 will also demonstrate the use of nonvolatile ferroelectric RAM which is inherently radiationtolerant. Lithium-ion polymer batteries are another state-of-the-art technology that will be employed offering high energy density for space applications. A novel, low-cost, low-power attitude control subsystem providing coarse, three-axis stabilization will also be implemented using only magnetic torquers as actuators and a three-axis magnetometer for sensor input. Experiments on-board NPSAT1 include two Naval Research Laboratory (NRL) payloads: the coherent electromagnetic radio tomography (CERTO) experiment and a Langmuir probe. The CERTO experiment is a radio beacon which, in concert with ground station receivers, is used to measure total-electron-content (TEC) in the ionosphere. The Langmuir probe will augment CERTO data by providing on-orbit measurements. The other experiments are of NPS origin. These include a configurable processor experiment (CPE), a COTS visible wavelength imager (VISIM), and a three-axis micro-electromechanical systems (MEMS)-based rate gyro. NPSAT1 is manifested on the Department of Defense Space Test Program (STP) MLV-05, Delta IV mission, due to launch in January 2006

Multi-Purpose Satellite Bus

This paper presents design considerations of a Multi-Purpose Satellite bus (MPS). The project was sponsored by the NASA Universities Space Research Association (USRA) Advanced Design Program. A multi-purpose satellite bus was selected as the study topic from a Statement-of-Work generated by the Defense Advanced Research Projects Agency. The estimated beginning-of-life weight of the MPS bus is 150 kg. A detailed analysis with two dissimilar payloads (a meteorological payload and a communication payload), both having a three year life, demonstrates the flexibility of the bus. The MPS bus was designed to mate with the Pegasus Air Launched Vehicle and the Taurus Standard Small Launch Vehicle. The satellite bus design is presented with emphasis on configuration requirements due to the dissimilar mission demands

Preliminary Design of the Naval Postgraduate School Petite Amateur Navy Satellite (PANSAT) Electric Power and Communications Subsystems

The Naval Postgraduate School\u27s (NPS) Space Systems Academic Group (SSAG) is continuing the design and development of the Petite Amateur Navy Satellite (PANSAT), a small communications satellite. The objectives of PANSAT are to provide: (i.) an educational tool for the officer students at NPS, (ii.) digital communications using spread spectrum in the amateur band, and (iii.) a low cost, space-based platform for small experiments. PANSAT is designed for an altitude of 480 km and an inclination greater than 28.5. The satellite weight is 150 Ibs and has no attitude control. The expected life of the satellite is 2 years. This paper discusses the preliminary design of the electrical power subsystem (EPS) and the communications subsystem (COMM). The BPS is a photovoltaic silicon cell system consisting of solar array, batteries, battery charge regulator (BCR) and DC to DC converters. The COMM payload uses direct sequence spread spectrum modulated BPSK with a 1 MHz bandwidth. The data rate is 1200 bps with a bit error rate of 10-5 with a 5 Watt output

Overview of the Naval Postgraduate School Petite Amateur Navy Satellite (PANSAT)

The Petite Amateur Navy Satellite (PANSAT) was launched aboard the STS-95 Discovery Shuttle. The historic Shuttle flight noted mainly by John Glenn\u27s return to space also marks the Naval Postgraduate School\u27s first small satellite in space. PANSAT, which is in a circular, low-Earth orbit (LEO), is the culmination of 50 officer students\u27 graduate theses over approximately a nine-year period. The satellite continues to support the educational mission at NPS and will soon provide on-orbit capability of store-and-forward digital communications for the amateur radio community using direct sequence, spread spectrum modulation. The spacecraft includes the communications payload, electrical power subsystem, digital control subsystem, and structure. This paper describes the overall architecture of the spacecraft bus, a discussion of the NPS command ground station, and some lessons learned

Naval Postgraduate School NPSAT1 Small Satellite

Paper presented at the ESA Small Satellite Systems and Services SymposiumThe NPSAT1 mission, conceived and developed by the Naval Postgraduate School (NPS) Space Systems Academic Group (SSAG), is sponsored and executed by the DoD Space Test Program (SMC SDD). The small satellite is manifested for launch aboard the STP-1 Atlas V Mission due to launch in December 2006. The main objective of the NPSAT1 program is to provide educational opportunities for the offi cer students in the Space Systems Curricula at NPS through the design, testing, integration, and fl ight operations of a small satellite. The 82 kg (180 lbs) satellite will be earth-pointing using a novel, low-cost, 3-axis attitude control scheme. NPSAT1 will provide a platform for a number of spacecraft technology experiments, including a lithium-ion battery, a confi gurable, fault-tolerant processor (CFTP) experiment, and fl ight demonstrations of commercial, off-the-shelf (COTS) components such as microelectromechanical systems (MEMS) rate sensors and a digital camera. The spacecraft command and data handling (C&DH) subsystem is NPS-designed, featuring low-power with error-detection-and-correction (EDAC) memory, an ARM720T microprocessor, and running Linux as the operating system. Two other experiments are provided by the Naval Research Laboratory to investigate ionospheric physics. This paper presents an overview of the spacecraft, its subsystems, and the challenges of a small satellite program in a university environment.Naval Postgraduate School, Monterey, California

Acoustic transparency in two-dimensional sonic crystals

Acoustic transparency is studied in two-dimensional sonic crystals consisting of hexagonal distributions of cylinders with continuously varying properties. The transparency condition is achieved by selectively closing the acoustic bandgaps, which are governed by the structure factor of the cylindrical scatterers. It is shown here that cylindrical scatterers with the proposed continuously varying properties are physically realizable by using metafluids based on sonic crystals. The feasibility of this proposal is analyzed by a numerical experiment based on multiple scattering theory.The work was partially supported by the Spanish MEC under Project no. TEC2007-67239. LWC acknowledges the financial support by the US National Science Foundation under grant CMS-0510940 and supplemental funding from the International Research and Education in Engineering (IREE) program. DT acknowledges a PhD grant paid by MEC. We also thank Helios Sanchis Alepuz for useful discussions.Sánchez-Dehesa Moreno-Cid, J.; Torrent, D.; Cai, L-W. (2009). Acoustic transparency in two-dimensional sonic crystals. New Journal of Physics. 11. https://doi.org/10.1088/1367-2630/11/1/013039S11Alù, A., & Engheta, N. (2005). Achieving transparency with plasmonic and metamaterial coatings. Physical Review E, 72(1). doi:10.1103/physreve.72.016623Alù, A., & Engheta, N. (2007). Plasmonic materials in transparency and cloaking problems: mechanism, robustness, and physical insights. Optics Express, 15(6), 3318. doi:10.1364/oe.15.003318Valentine, J., Zhang, S., Zentgraf, T., Ulin-Avila, E., Genov, D. A., Bartal, G., & Zhang, X. (2008). Three-dimensional optical metamaterial with a negative refractive index. Nature, 455(7211), 376-379. doi:10.1038/nature07247Li, J., & Chan, C. T. (2004). Double-negative acoustic metamaterial. Physical Review E, 70(5). doi:10.1103/physreve.70.055602Zhou, X., & Hu, G. (2007). Acoustic wave transparency for a multilayered sphere with acoustic metamaterials. Physical Review E, 75(4). doi:10.1103/physreve.75.046606Torrent, D., & Sánchez-Dehesa, J. (2007). Acoustic metamaterials for new two-dimensional sonic devices. New Journal of Physics, 9(9), 323-323. doi:10.1088/1367-2630/9/9/323Born, M., Wolf, E., Bhatia, A. B., Clemmow, P. C., Gabor, D., Stokes, A. R., … Wilcock, W. L. (1999). Principles of Optics. doi:10.1017/cbo9781139644181Sakoda, K. (2001). Optical Properties of Photonic Crystals. Springer Series in Optical Sciences. doi:10.1007/978-3-662-14324-7Cassagne, D., Jouanin, C., & Bertho, D. (1996). Hexagonal photonic-band-gap structures. Physical Review B, 53(11), 7134-7142. doi:10.1103/physrevb.53.7134Yasumoto, K., Toyama, H., & Kushta, T. (2004). Accurate Analysis of Two-Dimensional Electromagnetic Scattering From Multilayered Periodic Arrays of Circular Cylinders Using Lattice Sums Technique. IEEE Transactions on Antennas and Propagation, 52(10), 2603-2611. doi:10.1109/tap.2004.834440Sanchis, L., Håkansson, A., Cervera, F., & Sánchez-Dehesa, J. (2003). Acoustic interferometers based on two-dimensional arrays of rigid cylinders in air. Physical Review B, 67(3). doi:10.1103/physrevb.67.035422Cervera, F., Sanchis, L., Sánchez-Pérez, J. V., Martínez-Sala, R., Rubio, C., Meseguer, F., … Sánchez-Dehesa, J. (2001). Refractive Acoustic Devices for Airborne Sound. Physical Review Letters, 88(2). doi:10.1103/physrevlett.88.023902Krokhin, A. A., Arriaga, J., & Gumen, L. N. (2003). Speed of Sound in Periodic Elastic Composites. Physical Review Letters, 91(26). doi:10.1103/physrevlett.91.264302Torrent, D., Håkansson, A., Cervera, F., & Sánchez-Dehesa, J. (2006). Homogenization of Two-Dimensional Clusters of Rigid Rods in Air. Physical Review Letters, 96(20). doi:10.1103/physrevlett.96.204302Cai, L.-W. (2004). Multiple scattering in single scatterers. The Journal of the Acoustical Society of America, 115(3), 986-995. doi:10.1121/1.1643362Cai, L.-W., & Sánchez-Dehesa, J. (2008). Acoustical scattering by radially stratified scatterers. The Journal of the Acoustical Society of America, 124(5), 2715-2726. doi:10.1121/1.296782

Role of metabolically active hormones in the insulin resistance associated with short-term glucocorticoid treatment

BACKGROUND: The mechanisms by which glucocorticoid therapy promotes obesity and insulin resistance are incompletely characterized. Modulations of the metabolically active hormones, tumour necrosis factor alpha (TNF alpha), ghrelin, leptin and adiponectin are all implicated in the development of these cardiovascular risk factors. Little is known about the effects of short-term glucocorticoid treatment on levels of these hormones. RESEARCH METHODS AND PROCEDURES: Using a blinded, placebo-controlled approach, we randomised 25 healthy men (mean (SD) age: 24.2 (5.4) years) to 5 days of treatment with either placebo or oral dexamethasone 3 mg twice daily. Fasting plasma TNFα, ghrelin, leptin and adiponectin were measured before and after treatment. RESULTS: Mean changes in all hormones were no different between treatment arms, despite dexamethasone-related increases in body weight, blood pressure, HDL cholesterol and insulin. Changes in calculated indices of insulin sensitivity (HOMA-S, insulin sensitivity index) were strongly related to dexamethasone treatment (p < 0.001). DISCUSSION: Our data do not support a role for TNF alpha, ghrelin, leptin or adiponectin in the insulin resistance associated with short-term glucocorticoid treatment

Postmenopausal Hormone Therapy and Colorectal Cancer Risk by Molecularly Defined Subtypes and Tumor Location

Background: Postmenopausal hormone therapy (HT) is associated with a decreased colorectal cancer (CRC) risk. As CRC is a heterogeneous disease, we evaluated whether the association of HT and CRC differs across etiologically relevant, molecularly defined tumor subtypes and tumor location. Methods: We pooled data on tumor subtypes (microsatellite instability status, CpG island methylator phenotype status, BRAF and KRAS mutations, pathway: adenoma-carcinoma, alternate, serrated), tumor location (proximal colon, distal colon, rectum), and HT use among 8220 postmenopausal women (3898 CRC cases and 4322 controls) from 8 observational studies. We used multinomial logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CIs) for the association of ever vs never HT use with each tumor subtype compared with controls. Models were adjusted for study, age, body mass index, smoking status, and CRC family history. All statistical tests were 2-sided. Results: Among postmenopausal women, ever HT use was associated with a 38% reduction in overall CRC risk (OR =0.62, 95% CI = 0.56 to 0.69). This association was similar according to microsatellite instability, CpG island methylator phenotype and BRAF or KRAS status. However, the association was attenuated for tumors arising through the serrated pathway (OR = 0.81, 95% CI = 0.66 to 1.01) compared with the adenoma-carcinoma pathway (OR = 0.63, 95% CI = 0.55 to 0.73; P het =.04) and alternate pathway (OR = 0.61, 95% CI = 0.51 to 0.72). Additionally, proximal colon tumors had a weaker association (OR = 0.71, 95% CI = 0.62 to 0.80) compared with rectal (OR = 0.54, 95% CI = 0.46 to 0.63) and distal colon (OR = 0.57, 95% CI = 0.49 to 0.66; P het =.01) tumors. Conclusions: We observed a strong inverse association between HT use and overall CRC risk, which may predominantly reflect a benefit of HT use for tumors arising through the adenoma-carcinoma and alternate pathways as well as distal colon and rectal tumors