Interpretation of the N2 LBH glow observed on the S3-4 spacecraft

Emissions in the vacuum ultraviolet Lyman-Birge-Hopfield (LBH) bands of N2 were observed at night from the S3-4 spacecraft and from the Space Shuttle. No atmospheric source of this emission was identified. Conway et al. have reported that the intensity of the S3-4 LBH emission varied as the cube power of the N2 or N2O concentration. A vehicle-atmosphere interaction was suggested as the source but it was found that the needed excitation cross section would have to be unacceptably large. Recent models of the gas concentration build-up around large space vehicles predict concentrations that may be consistent with the observe LBH intensity variation with altitude. The emission in the model is generated primarily by secondary collisional excitation by ambient N2 and/or O of desorbed metastable molecular constituents. A Chapman-like production function in the induced gaseous environment results in the observed cube power of the N2 concentration altitude variation. A cross section of approximately 2.5 x 10(-18) sq cm is required for excitation of desorbed metastable N2(A) to the N2 (a 1 Pi g) state to account for the observed intensities

A possible glow experiment for the EOM 1-2 mission

A possible opportunity for study of surface glow exists during the Environmental Observation Mission (EOM) 1-2 mission scheduled for launch on September 3, 1986. The EOM 1-2 payload includes spectroscopic and photometric instruments which operate in wavelength regions of great interest to the glow assessment activity. However, as in the case of many remote sensing instruments, these are located in the payload bay in such a way as to avoid viewing any shuttle or payload surfaces. If these instruments are to measure the spectral characteristics of surfaces, it is necessary for such surfaces to be positioned in the field of view of these instruments for the duration of the particular measurement sequence. It is possible that the shuttle of which the EOM 1-2 payload flies will have an Remote Manipulator System (RMS) in place. An assessment has shown that it is indeed feasible to place a four-sided cuff around the end of the RMS. The four sides, each coated with a different material, can then be positioned in turn above the instruments, and in such a way that the surface is alternately pointed into the ram and into the wake

An Imaging Spectrometric Observatory (ISO)

The Imaging Spectrometric Observatory (ISO) is designed for low light level spectroscopy of both the day and night side of the earth. The instrument is composed of five spectrometers, each of which covers part of the total wavelength range of 30 to 1300 nm spanned by the instrument. Wavelength resolution varies between 0.2 and 0.6 nm over the spectral range. The five spectrometers are each optimized for a portion of the spectrum by the choice of mirror reflective coatings and detector photocathode materials. The full spectral range for each spectrometer is covered in a total of 11 grating steps. The Imaging Spectrometric Observatory was flown for the first time on the Spacelab 1 mission during which it acquired almost 40 hr of observations. The ISO investigation to be flown on the Atmospheric Laboratory for Applications and Science (ATLAS 1) mission will draw on the experience gained from the data gathered on Spacelab 1. The detector system in each spectrometer was upgraded to provide both higher sensitivity at low light levels and simultaneous imaging over larger spectral segments than was achieved on Spacelab 1. In addition, the instrument and the observing sequences were modified to allow observation of the sun in the extreme ultraviolet. A summary of ISO parameters for ATLAS 1 (scheduled for late 1990) is given

Enhanced N(+) Sub 2 in the Shuttle Environment

Observations were made of the N2 first negative and Meinel emission bands with the Imaging Spectrometric Observatory (ISO) on Spacelab 1. These observations have revealed the presence of N2 emissions which exceed those expected on the basis of current ionospheric models by up to a factor of 10. If the emission is of terrestrial origin, large unidentified ionospheric sources of N2 ions must exist. On the other hand, if the source is local to the shuttle environment, a mechanism must be found which is capable of generating emissions of such unexpectedly large intensity. Charge exchange of ambient ionospheric O+ ions with shuttle environmental N2, followed by resonance scattering of sunlight, as a candidate were suggested. However, this model implies that a cloud of N2 gases must surround the vehicle in concentrations in excess of 10 to the 11 c.c. cm with a scale length of tens of meters. In addition, the N2 residence time must be of the order of 10 sec

Technique to retrieve solar EUV flux and neutral thermospheric O, O2, N2, and temperature from airglow measurements

We describe a method for retrieving neutral thermospheric composition and solar EUV flux from optical measurements of the O(+)(P-2) 732 nm and O(D-1) 630 nm airglow emissions. The parameters retrieved are the neutral temperature, the O, L2, and N2 density profiles, and a scaling factor for the solar EUV flux spectrum. The temperature, solar EUV flux scaling factor, and atomic oxygen density are first retrieved from the 732 nm emission, which are then used with the 630 nm emission to retrieve the O2 and N2 densities. Between the altitudes of 200 and 400 km the retrieval technique is able to statistically retrieve values to within 3.1% for thermospheric temperature, 3.3% for atomic oxygen, 2.3% for molecular oxygen, and 2.4% for molecular nitrogen. The solar EUV flux scaling factor has a retrieval error of 5.1%. We also present the results of retrievals using existing data taken from both groundbased and spacebased instruments. These include airglow data taken by the Visible Airglow Experiment on the Atmospheric Explorer spacecraft and the Imaging Spectrometric Observatory flown on the ATLAS 1 shuttle mission in 1992

How do tsetse recognise their hosts? The role of shape in the responses of tsetse (Glossina fuscipes and G. palpalis) to artificial hosts

Palpalis-group tsetse, particularly the subspecies of Glossina palpalis and G. fuscipes, are the most important transmitters of human African trypanomiasis (HAT), transmitting .95% of cases. Traps and insecticide-treated targets are used to control tsetse but more cost-effective baits might be developed through a better understanding of the fly’s host-seeking behaviour.Electrocuting grids were used to assess the numbers of G. palpalis palpalis and G. fuscipes quanzensis attracted to and landing on square or oblong targets of black cloth varying in size from 0.01 m2 to 1.0 m2. For both species, increasing the size of a square target from 0.01 m2 (dimensions = 0.1 x 0.1 m) to 1.0 m2 (1.0 x 1.0 m) increased the catch ,4x however the numbers of tsetse killed per unit area of target declined with target size suggesting that the most cost efficient targets are not the largest. For G. f. quanzensis, horizontal oblongs, (1 m wide x 0.5 m high) caught, 1.8x more tsetse than vertical ones (0.5 m wide x 1.0 m high) but the opposite applied for G. p. palpalis. Shape preference was consistent over the range of target sizes. For G. p. palpalis square targets caught as many tsetse as the oblong; while the evidence is less strong the same appears to apply to G. f. quanzensis. The results suggest that targets used to control G. p. palpalis and G. f. quanzensis should be square, and that the most cost-effective designs, as judged by the numbers of tsetse caught per area of target, are likely to be in the region of 0.25 x 0.25 m2. The preference of G. p. palpalis for vertical oblongs is unique amongst tsetse species, and it is suggested that this response might be related to its anthropophagic behaviour and hence importance as a vector of HAT

Is the even distribution of insecticide-treated cattle essential for tsetse control? Modelling the impact of baits in heterogeneous environments

Background: Eliminating Rhodesian sleeping sickness, the zoonotic form of Human African Trypanosomiasis, can be achieved only through interventions against the vectors, species of tsetse (Glossina). The use of insecticide-treated cattle is the most cost-effective method of controlling tsetse but its impact might be compromised by the patchy distribution of livestock. A deterministic simulation model was used to analyse the effects of spatial heterogeneities in habitat and baits (insecticide-treated cattle and targets) on the distribution and abundance of tsetse. Methodology/Principal Findings: The simulated area comprised an operational block extending 32 km from an area of good habitat from which tsetse might invade. Within the operational block, habitat comprised good areas mixed with poor ones where survival probabilities and population densities were lower. In good habitat, the natural daily mortalities of adults averaged 6.14% for males and 3.07% for females; the population grew 8.46in a year following a 90% reduction in densities of adults and pupae, but expired when the population density of males was reduced to <0.1/km2; daily movement of adults averaged 249 m for males and 367 m for females. Baits were placed throughout the operational area, or patchily to simulate uneven distributions of cattle and targets. Gaps of 2–3 km between baits were inconsequential provided the average imposed mortality per km2 across the entire operational area was maintained. Leaving gaps 5–7 km wide inside an area where baits killed 10% per day delayed effective control by 4–11 years. Corrective measures that put a few baits within the gaps were more effective than deploying extra baits on the edges. Conclusions/Significance: The uneven distribution of cattle within settled areas is unlikely to compromise the impact of insecticide-treated cattle on tsetse. However, where areas of >3 km wide are cattle-free then insecticide-treated targets should be deployed to compensate for the lack of cattle

Optimizing the colour and fabric of targets for the control of the tsetse fly Glossina fuscipes fuscipes

Background: Most cases of human African trypanosomiasis (HAT) start with a bite from one of the subspecies of Glossina fuscipes. Tsetse use a range of olfactory and visual stimuli to locate their hosts and this response can be exploited to lure tsetse to insecticide-treated targets thereby reducing transmission. To provide a rational basis for cost-effective designs of target, we undertook studies to identify the optimal target colour. Methodology/Principal Findings: On the Chamaunga islands of Lake Victoria , Kenya, studies were made of the numbers of G. fuscipes fuscipes attracted to targets consisting of a panel (25 cm square) of various coloured fabrics flanked by a panel (also 25 cm square) of fine black netting. Both panels were covered with an electrocuting grid to catch tsetse as they contacted the target. The reflectances of the 37 different-coloured cloth panels utilised in the study were measured spectrophotometrically. Catch was positively correlated with percentage reflectance at the blue (460 nm) wavelength and negatively correlated with reflectance at UV (360 nm) and green (520 nm) wavelengths. The best target was subjectively blue, with percentage reflectances of 3%, 29%, and 20% at 360 nm, 460 nm and 520 nm respectively. The worst target was also, subjectively, blue, but with high reflectances at UV (35% reflectance at 360 nm) wavelengths as well as blue (36% reflectance at 460 nm); the best low UV-reflecting blue caught 3× more tsetse than the high UV-reflecting blue. Conclusions/Significance: Insecticide-treated targets to control G. f. fuscipes should be blue with low reflectance in both the UV and green bands of the spectrum. Targets that are subjectively blue will perform poorly if they also reflect UV strongly. The selection of fabrics for targets should be guided by spectral analysis of the cloth across both the spectrum visible to humans and the UV region

A far ultraviolet imager for the International Solar-Terrestrial Physics Mission

The aurorae are the result of collisions with the atmosphere of energetic particles that have their origin in the solar wind, and reach the atmosphere after having undergone varying degrees of acceleration and redistribution within the Earth's magnetosphere. The global scale phenomenon represented by the aurorae therefore contains considerable information concerning the solar-terrestrial connection. For example, by correctly measuring specific auroral emissions, and with the aid of comprehensive models of the region, we can infer the total energy flux entering the atmosphere and the average energy of the particles causing these emissions. Furthermore, from these auroral emissions we can determine the ionospheric conductances that are part of the closing of the magnetospheric currents through the ionosphere, and from these we can in turn obtain the electric potentials and convective patterns that are an essential element to our understanding of the global magnetosphere-ionosphere-thermosphere-mesosphere. Simultaneously acquired images of the auroral oval and polar cap not only yield the temporal and spatial morphology from which we can infer activity indices, but in conjunction with simultaneous measurements made on spacecraft at other locations within the magnetosphere, allow us to map the various parts of the oval back to their source regions in the magnetosphere. This paper describes the Ultraviolet Imager for the Global Geospace Sciences portion of the International Solar-Terrestrial Physics program. The instrument operates in the far ultraviolet (FUV) and is capable of imaging the auroral oval regardless of whether it is sunlit or in darkness. The instrument has an 8° circular field of view and is located on a despun platform which permits simultaneous imaging of the entire oval for at least 9 hours of every 18 hour orbit. The three mirror, unobscured aperture, optical system ( f /2.9) provides excellent imaging over this full field of view, yielding a per pixel angular resolution of 0.6 milliradians. Its FUV filters have been designed to allow accurate spectral separation of the features of interest, thus allowing quantitative interpretation of the images to provide the parameters mentioned above. The system has been designed to provide ten orders of magnitude blocking against longer wavelength (primarily visible) scattered sunlight, thus allowing the first imaging of key, spectrally resolved, FUV diagnostic features in the fully sunlit midday aurorae. The intensified-CCD detector has a nominal frame rate of 37 s, and the fast optical system has a noise equivalent signal within one frame of ∼ 10 R . The instantaneous dynamic range is >1000 and can be positioned within an overall gain range of 10 4 , allowing measurement of both the very weak polar cap emissions and the very bright aurora. The optical surfaces have been designed to be sufficiently smooth to permit this dynamic range to be utilized without the scattering of light from bright features into the weaker features. Finally, the data product can only be as good as the degree to which the instrument performance is characterized and calibrated. In the VUV, calibration of an an imager intended for quantitative studies is a task requiring some pioneering methods, but it is now possible to calibrate such an instrument over its focal plane to an accuracy of ±10%. In summary, very recent advances in optical, filter and detector technology have been exploited to produce an auroral imager to meet the ISTP objectives.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43777/1/11214_2004_Article_BF00751335.pd