Coarse attitude determination from Earth albedo measurements

Attitude estimation algorithms for the Thrusted Vector Mission which determine attitude based on Sun sensor and very coarse albedo sensor measurements are presented. On the basis of these measurements, it has been demonstrated by comparison with more accurate gyro-based attitude that it is possible to estimate three-axis attitude with an average error per axis of 11 deg. Most of this error is about the Sun direction. Both deterministic quick-look and optimal estimates are examined     

OSIRIS-REx low-velocity particles during outbound cruise

We analyzed high-angular rate streaks first recorded by OSIRIS-REx’s MapCam during a 2017 search for Earth Trojan asteroids. We interpret them as water-ice particles that translated across the imager’s field of view, originating from the spacecraft itself. Their translation velocities approximated 0.1–1?m/s based on reasonable conclusions about their range. Pursuing several lines of investigation to seek a coherent hypothesis, we conclude that the episodic releases of the water ice particles are associated with spacecraft attitudes that resulted in solar illumination of previously shadowed regions. This correlation suggests that the OSIRIS-REx spacecraft itself possesses micro-climatic zones consisting of hot regions and cold traps that may temporarily potentially pass volatiles back and forth before losing most of them.     

Spartan 201 white light coronagraph experiment

A white light coronagraph was launched into orbit aboard the space shuttle OV 103 (Discovery) on 7 April 1993. This device was one of two instruments included in the SPARTAN 201-1 payload, a completely autonomous sub-satellite deployed from the shuttle for a period of about 47 hours. The WLC system is an externally occulted coronagraph system which incorporates a rotating half-wave plate polarimeter, and the image data is used to infer the brightness, the polarized brightness and the degree of polarization of the white light emission from the solar corona. These data are in turn used to infer estimates of the K- and F-coronal brightnesses and density distributions. We shall present preliminary results of the electron density estimate in the coronal streamer and hole region and describe the methods employed.affiliated to USRA     

Loran-C cycle identification in hard-limiting receivers

A new technique is presented for use in hard-limiting receivers. It is based on the widely used analogue “half-cycle peak ratio” (HCPR) technique, from which it differs by being entirely digital; no additional analogue signal processing or other hardware is required. Drawing on recent advances, the new method makes decisions based on a large number of sample points in each Loran-C pulse, thereby increasing the resilience of the identification process in the presence of noise. Performance of the algorithm in the face of continuous-wave interference is equal to or better than that of other cycle-identification techniques     

Can incineration technology convert CELSS wastes to resources for crop production? A working hypothesis and some preliminary findings.

Considerable evidence exists to support the hypothesis that human-generated wastes can be utilized as resources in crop production. In the waste mix from a Closed Ecological Life Support System (CELSS), the elemental resources are found mainly in the solid fraction. In order to make these resources available for crop growth, it is necessary to convert the solid wastes to either an aqueous or a gaseous phase. Incineration is one method for processing solid wastes to produce a gaseous fraction and a small solid fraction of ash. Evidence from literature provides a compelling case for a working hypothesis that plants can utilize the gases of incineration. Although uptake and utilization of inorganic elements in the aqueous phase is well established, the uptake and utilization of inorganic elements in the gaseous phase, with the exception of CO2 and O2, is not fully understood. This paper attempts to (a) summarize existing literature on uptake/metabolism of inorganic elements in the gaseous fraction, with the exception of CO2 and O2 and (b) develop a working hypothesis to predict the use of incineration flue gases by plants. Preliminary experimental findings on effects of carbon monoxide, a component of the flue gas, are also presented.     

A new technique for decoding Loran-C radionavigation signals

A new approach to the extraction of navigation information from Loran-C radionavigation signals is described. A reduced-rate time-reversed sequence is derived from the RF signal and processed by a finite-impulse response (FIR) filter. It is shown that proper design of the FIR filter and proper control of the sampling point guarantee the rejection of skywave contamination, and achieve excellent rejection of continuous-wave interference (CWI). The process is computationally efficient     

Multiple model adaptive estimation with filter spawning

Multiple model adaptive estimation (MMAE) with filter spawning is used to detect and estimate partial actuator failures on the VISTA F-16. The truth model is a full six-degree-of-freedom simulation provided by Calspan and General Dynamics. The design models are chosen as 13-state linearized models, including first order actuator models. Actuator failures are incorporated into the truth model and design model assuming a "failure to free stream." Filter spawning is used to include additional filters with partial actuator failure hypotheses into the MMAE bank. The spawned filters are based on varying degrees of partial failures (in terms of effectiveness) associated with the complete-actuaton-failure hypothesis with the highest conditional probability of correctness at the current time. Thus, a blended estimate of the failure effectiveness is found using the filters' estimates based upon a no-failure hypothesis, a complete actuator failure hypothesis, and the spawned filters' partial-failure hypotheses. This yields substantial precision in effectiveness estimation, compared with what is possible without spawning additional filters, making partial failure adaptation a viable methodology.     

Coronal mass-ejection events

Nearly fifteen years have passed since the discovery of coronal mass ejection events from the solar atmosphere. Progress in the interpretation of the observational results has led to a body of knowledge concerning the geometrical and evolutionary properties, physical characteristics, and the association of this type of event with other forms of solar activity. Recent interpretive results taken from the large body of observational data now available are discussed below in some detail. A classification system based on kinetic properties of these events is presented.     

Instrumentation and data systems for high-time resolution study of space plasma shocks

This paper deals with the principal methods of achieving high-time resolution measurements for the study of fine structure of shocks and other discontinuities in space plasmas. In the measurements of ion energy spectra, we have obtained the time resolution about 1s.In the Soviet-Czechoslovak INTERSHOCK project we will obtain temporal resolution better than 0.1s in the measurement of the main plasma parameters. This will be obtained with the multichannel energy spectrometer and the on-board data acquisition and processing system triggered by the shock signature. This system controls the data sampling rate from some scientific instruments and switches on a high-sampling rate near the shock. The method implies detecting a shock by means of on-board processing of magnetic field and plasma parameters. The algorithm for this detection uses both parameters separately as well as in combinations.     

The OSIRIS-REx Thermal Emission Spectrometer (OTES) Instrument

The OSIRIS-REx Thermal Emission Spectrometer (OTES) will provide remote measurements of mineralogy and thermophysical properties of Bennu to map its surface, help select the OSIRIS-REx sampling site, and investigate the Yarkovsky effect. OTES is a Fourier Transform spectrometer covering the spectral range 5.71–100 μm (\(1750\mbox{--}100~\mbox{cm}^{-1}\)) with a spectral sample interval of \(8.66~\mbox{cm}^{-1}\) and a 6.5-mrad field of view. The OTES telescope is a 15.2-cm diameter Cassegrain telescope that feeds a flat-plate Michelson moving mirror mounted on a linear voice-coil motor assembly. A single uncooled deuterated l-alanine doped triglycine sulfate (DLATGS) pyroelectric detector is used to sample the interferogram every two seconds. Redundant ～0.855 μm laser diodes are used in a metrology interferometer to provide precise moving mirror control and IR sampling at 772 Hz. The beamsplitter is a 38-mm diameter, 1-mm thick chemical vapor deposited diamond with an antireflection microstructure to minimize surface reflection. An internal calibration cone blackbody target provides radiometric calibration. The radiometric precision in a single spectrum is \(\leq2.2 \times 10^{-8}~\mbox{W}\,\mbox{cm}^{-2}\,\mbox{sr} ^{-1}/\mbox{cm}^{-1}\) between 300 and \(1350~\mbox{cm}^{-1}\). The absolute integrated radiance error is \(<1\%\) for scene temperatures ranging from 150 to 380 K. The overall OTES envelope size is \(37.5 \times 28.9 \times 52.2~\mbox{cm}\), and the mass is 6.27 kg. The power consumption is 10.8 W average. OTES was developed by Arizona State University with Moog Broad Reach developing the electronics. OTES was integrated, tested, and radiometrically calibrated on the Arizona State University campus in Tempe, AZ.