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The SAAO observing station near Sutherland, Northern Cape Province (NCP), South Africa, is among observatories with the darkest skies in the world. It is home to many national and international optical and IR telescopes, including SALT. The NCP is declared as Astronomy Advantage Area, and therefore regulated under the Astronomy Geographic Advantage Act of 2007, which empowers the Department of Science and Innovation minister to regulate activities that pose a threat to optical and/or radio astronomy within the declared areas. In May 2019, the Sutherland Central Astronomy Advantage Area (SCAAA) protection regulations aimed at protecting optical astronomy and related endeavours at SAAO against activities negatively impacting on astronomy within the SCAAA (75 km radius from SALT in the NCP), were promulgated. We discuss these regulations, including monitoring of light pollution and other activities that may have negative impact on astronomy at SAAO, regulatory implementation and compliance, as well as current and potential challenges, and lessons learned so far. The night sky brightness measurements collected over the past five years with the All Sky Transmission MONitors (ASTMONs) at Sutherland are presented for the first time, and they indicate that the quality of the night sky at SAAO has not changed for the worst going as far back as the 1980s. The current average sky brightness measurements from the ASTMONs are consistent with historical night sky brightness measurements collected with the SAAO telescopes over the past 40 years. The results also confirm that Sutherland is globally a very dark observatory site.

Though the sun is our most abundant source of energy, existing solar power production methods can generate electricity only while the sun is shining. To shift to a truly sustainable energy grid, new green energy production techniques that function at night must be developed. Here we consider a “nighttime photovoltaic cell” that harnesses electricity from the flow of heat between the earth and the cold night sky. We discuss thermoradiative photovoltaics, the physics driving this photovoltaic technique, and the theoretical limits of such a device. We conclude with an analysis of this novel photovoltaic concept’s practical limits and integrability.

Maunakea Spectroscopic Explorer (MSE) is the first of the future generation of massively multiplexed spectroscopic 11.25m mirror facility on a recycled site. MSE is designed to enable transformative science, being completely dedicated to large-scale multi-object spectroscopic surveys, each studying thousands to millions of astrophysical objects. MSE’s transformational potential lies in answering numerous scientific questions and finding new puzzles. Its success will depend in part on its ability to detect large populations of faint sources, from those responsible for reionization to merging galaxies at cosmic dawn and the stellar populations of nearby dwarf galaxies. This capability is set, in part, by our ability to remove the sky from the target spectra. Here we describe the initial steps in a threeyear long effort to develop a model of the Maunakea skies comparable to the model developed by ESO of the southern ESO sites. The model will be used to derive best-practices (e.g. the number of required fibers given specific observing conditions, and required sensitivity) and sky subtraction algorithms to achieve << 1% sky subtraction accuracy

Fireball camera networks are being pursued all over the world and continuously monitor the night sky for fire- balls produced as larger meteoroids enter the Earth’s atmosphere at high speeds. As well, in Morocco we have a new detection network calling MOFID network (Moroccan Observatory For Fireball Detection), which is a cooperation with the team of DFN network (Desert Fireball Network) in Australia. The first dual detection with the MOFID network was captured on December 25 at 19:32 local time (18:32 UTC) (lasted about 3.4 seconds).

Telescopes suffer from radiative subcooling against the night sky (“low-wind effect”), depending on wind speed, sky exposure and the emissivity of the surface finish. Critical structural elements in the ELT are the spider vanes, the vertical trusses in the telescope tube and the M4 Tower. We present an improved sky temperature model and 3D computational fluid dynamics simulations of the airflow inside the ELT dome with local temperatures and derive the wavefront error map in the pupil from it, using ray tracing. We discuss the optimal shape that M4 can achieve to correct the errors and report the wavefront residuals.

The work continues the research started in 2017. In 2018 in addition to constant monitoring of the night sky glow, a series of experiments were carried out to register fast variations in the spatial intensity distribution of the night sky radiation in the spectral range of 400–900 nm by an optical instruments complex. The devices complex includes: A photometer assembled on the basis of SONY ICX285AL CCD matrix and a high-aperture lens Jupiter 3; Highly sensitive optical system created on the basis of the 3rd generation EPM102G-04-22C electron-optical converter (EOC) and the Baumer HXG40NIR camera based on CMOSIS CMV4000 1 matrix; Fast four-channel photometer with sensors based on silicon photomultipliers. The paper presents the results of experiments on the synchronous observation of fast optical phenomena in the Earth’s atmosphere. The number of events recorded simultaneously on multiple devices is given. We describe methods and algorithms for extracting events from data series.

The aurora is a beautiful night sky optical phenomenon that is readily seen at high-latitude locations, but with more effort can also be seen and enjoyed at mid-latitude locations. Guidelines for when and where to look are presented, along with a rich array of photographic examples of mid-latitude auroras exhibiting all the usual range of green, red, and purple colors.

With the emergence of Shortwave Infrared (SWIR) InGaAs detector arrays, designers of electro-optical imaging systems can take advantage of the reduced Rayleigh scattering of the SWIR band when compared to visible, resulting in higher contrast images through haze, mist, rain, fog and challenging atmospheric conditions. Furthermore, from a military standpoint, SWIR is invisible to the human eye, thus enabling covert operations and is a good choice for targeting with laser rangefinders and designators that transmits between 1060 nm and 1570 nm. A SWIR sensor can also be used in night vision applications taking advantage of an atmospheric phenomenon called night sky radiance (or night glow) that emits five to seven times more illumination than starlight, nearly all of it in the SWIR wavelengths. In a typical airborne application a sensor’s performance is mechanically constrained by the space/volume available and the aperture size limit. This paper describes a model based trade-off methodology to select the optimal Field of View (FOV) for an aperture limited SWIR sensor. This method balances the influences FOV has on sensitivity and resolution. The SWIR sensor’s performance is optimized within mechanical constraints and for the intended application scenarios. In the SWIR band the analysis is expanded to include night time scenarios and laser “see-spot” performance. This model is also adapted for input variable compliance with the industry standard NV-IPM range performance model1 enabling cross-correlation between the two model’s results. An example of a SWIR sensor analysis applying this design model is presented, highlighting the performance advantages that can be gained by maximizing the aperture utilization and choosing the optimal FOV for an imaging sensor when used in airborne targeting applications.

The Wumingshan mountain (Mt. WMS), located in the Grand Shangri-La area of south-west China, has been selected as one of the most potential regions for hosting China’s next-generation ground-based large telescopes. Firstly, Mt. WMS has ideal astronomical conditions for both day-time and night-time observations. Comprehensive analysis of remote and on-site long-term meteorological, geological and geographic data suggests that WMS satisfies the strict requirements for an excellent candidate site, through a series of key parameters including average seeing factor r0, sky brightness, clear-sky days, precipitable water vapor content (PWVC), refractive index structure constant, atmospheric coherence time, isoplanatic angle and meteorological information etc. Averagely, its daily seeing factor is over 10 cm and its night seeing factor is 0.9 arcsec on ground. The average wind speed is less than 5 m/s. The average normalized PWVC at unit air mass is about 2.5 mm. The average yearly sunshine duration is generally more than 2500 hours. The amount of yearly clear sky days and nights are respectively 250 d and 270 d. The median night sky brightness level is 21.8 mag arcsec-2. The atmosphere cleanliness is also excellent. Secondly, Mt. WMS possesses the necessary conditions for the establishment of high altitude observatories. Its ridge is flat and spreads over 2 km2. The large relative elevation difference in the local terrain, plus the existence of population settlements at low altitude (~ 2800 m) in the vicinity, substantially reduces the future cost for construction, settlement, and logistics. Its geological structure is stable, and there is virtually no record of geological disaster or inclement weather. The nearby counties have low population density (~5 km-2) and there have been extensive transportation networks. In October 2014, we initiated a long-term monitoring project in Mt. WMS. We have been collecting data from two monitoring sites for more than three years. Both sites are located about 4700~4800 m above the sea level. Our instruments mainly include the solar and stellar Differential Image Motion Monitors, the Sky Brightness Monitors, the PWVC monitors, the Atmospheric Temperature Fluctuation Monitors, the Multi-wavelength Solar Photometers and robot meterological stations, and so on. There have been a lot of activities within the ASO-G (i.e., CGST and large coronagraph) sites’ study since our last reports.1, 2 In this paper, we introduce the daily observation, transmission, storage and analysis of the harvested data, and the overall operation, management and technical support of the monitoring platforms.

Given enough exposure time the sensitivity of an astronomical instrument is ultimately limited by systematic errors, and the dominant source of systematic errors for most optical/infrared instruments is imperfect sky subtraction. In turn the limiting factor for sky subtraction accuracy is frequently the accuracy of flat field calibration, making these calibrations critical to the overall performance of the instrument. The Anglo-Australian Telescope’s fibre-fed spectrographs, and in particular the multi-object integral field spectrograph SAMI, are reaching sky subtraction systematic error limits and this has motivated an upgrade to the calibration systems. SAMI and its successor HECTOR are calling for sky subtraction accuracies of at least 0.25%, with a goal of 0.06%, an improvement of 4-17 times. Flat field calibrations can use dark sky, twilight sky or an illuminated screen (‘dome flats’). For multi-object spectrographs such as SAMI recalibration is required for each set of targets. This makes twilight flats impractical as it is impossible to guarantee the availability of clear twilight sky for every configuration. The dark night sky is the ideal calibrator, but the long integration times required result in onerous overheads. What is needed is a dome flat field system accurate enough to replace dark sky flats. To achieve this we have replaced both the existing screen and its illumination system. The effective throughput of optical fibres feeding an instrument vary slightly as their paths change, so high accuracy demands that calibration be done with the telescope in the same position as the science observations. We have applied two new screens to the dome windscreen, either side of the aperture, so that it is possible to move a screen in front of the telescope while in any position. There are two distinct purposes for flat fielding: photometric calibration and sky subtraction. For an ideal telescope these are equivalent but the existence of stray light creates subtle differences, and this has implications for design of the screen. When the primary purpose is sky subtraction the highest possible accuracy will be achieved with a screen that illuminates the telescope from all the directions that the night sky does. Consequently our screens match the size, shape and relative position of the windscreen aperture. The screens are implemented as Avian D diffuse reflectance coating applied to the dome windscreen itself. Avian D is highly Lambertian, has high reflectance and is durable enough for the observatory environment. The screens must be illuminated uniformly, in terms of spatial variations of both total intensity and spectral energy distribution (SED). We use an array of lamps around the end of the telescope tube. By using LEDs we are able to customise the SED and obtain a signal to noise ratio that is more consistent across wavelengths than is possible with traditional quartz tungsten halogen flat field lamps. We present the design of the new flat field calibration system, explain the main design decisions and discuss results from commissioning. These include comparisons between dome and dark sky flats, and measurements of the sky subtraction accuracy.

A modern implementation of a stellar intensity interferometry (SII) system on an array of large optical telescopes would be a highly valuable complement to the current generation of optical amplitude interferometers. The SII technique allows for observations at short optical wavelengths (U/B/V bands) with potentially dense (u,v) plane coverage. We describe a complete SII system that is used to measure the spatial coherence of a laboratory source which exhibits signal to noise ratios comparable to actual stellar sources. A novel analysis method, based on the correlation measurements between orthogonal polarization states, was developed to remove unwanted effects of spurious correlations. Our system is currently being tested in night sky observations at the StarBase Observatory (Grantsville, Utah) and will soon be ported to the VERITAS (Amado, AZ) telescopes. The system can readily be integrated with current optical telescopes at minimal cost. The work here serves as a technological pathfinder for implementing SII on the future Cherenkov Telescope Array.

We present preliminary observational results of short-period variations in the night sky airglow at middle latitudes. Observations were performed by using a CCD-based photometer over 2016 December to 2017 March. The main objective of our study is to determine a possibility of using a CCD camera to record fast optical flashes, and check a capability to separate signals from satellites, meteors, ground lightning discharges, etc. We describe automatic algorithms to select a frame with a flash and to identify the flash type. Based on the primary database of flashes, a preliminary statistical analysis of the results of observations was performed.

The SED16 is an autonomous multi-missions star tracker which delivers three axis satellite attitude in an inertial reference frame and the satellite angular velocity with no prior information. The qualification process of this star sensor includes five validation steps using optical star simulator, digitized image simulator and a night sky tests setup. The night sky testing was the final step of the qualification process during which all the functions of the star tracker were used in almost nominal conditions : Autonomous Acquisition of the attitude, Autonomous Tracking of ten stars. These tests were performed in Calern in the premises of the OCA (Observatoire de la Cote d’Azur). The test set-up and the test results are described after a brief review of the sensor main characteristics and qualification process.

The observatory Lovozero (68.0N, 35.0E, Polar Geophysical Institute) carries out regular observations of aurora. During the aurora observations in some cases the luminescence of the night sky had a wavy structure with the wavelengths of several tens kilometers and with the temporary periods about 15-30 minutes. For two cases comparisons with data of the radar of partial reflections in the observatory Tumanny have been carried out. Maxima of reflection amplitudes of the radar took place at the heights of 80-90 km and amplitudes at these heights had the periods similar to the periods of fluctuations of luminous intensity of the sky. It allows assuming that the wave structures in the luminescence were caused by acoustic-gravity waves.

The Havemann-Taylor Fast Radiative Transfer Code (HT-FRTC) represents transmittances, radiances and fluxes by principal components that cover the spectra at very high resolution, allowing fast highly-resolved pseudo line-by-line, hyperspectral and broadband simulations across the electromagnetic spectrum form the microwave to the ultraviolet for satellite-based, airborne and ground-based sensors. HT-FRTC models clear atmospheres and those containing clouds and aerosols, as well as any surface (land/sea/man-made). The HT-FRTC has been used operationally in the NEON Tactical Decision Aid (TDA) since 2008. The TDA combines the HT-FRTC with a thermal contrast model and an NWP model forecast data feed to predict the apparent thermal contrast between different surfaces and ground-based targets in the thermal and short-wave IR. The new objective here is to predict the optical contrast of air-borne targets under realistic night-time scenarios in the Photopic and NVG parts of the spectrum. This requires the inclusion of all the relevant radiation sources, which include twilight, moonlight, starlight, airglow and cultural light. A completely new exact scattering code has been developed which allows the straight-forward addition of any number of direct and diffuse sources anywhere in the atmosphere. The new code solves the radiative transfer equation iteratively and is faster than the previous solution. Simulations of scenarios with different light levels, from situations during a full moon to a moonless night with very low light levels and a situation with cultural light from a town are presented. The impact of surface reflectance and target reflectance is investigated.

Light pollution has become a prominent issue, specifically in National Parks such as Yosemite, where visitors go to enjoy the natural ‘night sky’. In an effort to reduce light pollution, a particularly obtrusive light source has been selected for retrofit. Using nonimaging optics and light emitting diodes (LEDs), light can be controlled to achieve a desired prescribed illumination distribution. This distribution possesses a sharp cut-off such that light leakage is minimal. Nonimaging optical designs are 3D printed, retrofitted into the candidate fixture, and tested in Yosemite National Park. The end goal is to drastically reduce and even eliminate the excess light from sources around the park.

We report on the proton radiation effects on a 1k x 1k e2v EMCCD utilized in the Nuvu EM N2 1024 camera. Radiation testing was performed at the TRIUMF Proton Irradiation Facility in Canada, where the e2v CCD201-20 EMCCD received a 105 MeV proton fluence up to 5.2x109 protons/cm2, emulating a 1 year’s radiation dose of solar protons in low earth orbit with nominal shielding that would be expected from a small or microsatellite. The primary space-based application is for Space Situational Awareness (SSA), where a small telescope images faint orbiting Resident Space Objects (RSOs) on the EMCCD, resulting in faint streaks at the photon level of signal in the images. Of particular concern is the effect of proton radiation on low level CTE, where very low level signals could be severely impaired if not lost. Although other groups have reported on the characteristics of irradiated EMCCDs, their CTE results are not portable to this application. To understand the real impact of proton irradiation the device must be tested under realistic operating conditions with representative backgrounds, clock periods, and signal levels. Testing was performed both in the laboratory and under a night sky on the ground in order to emulate a complex star background environment containing RSOs. The degradation is presented and mitigation techniques are proposed. As compared to conventional CCDs, the EMCCD with high gain allows faint and moving RSOs to be detected with a relatively small telescope aperture, at improved signal to noise ratio at high frame rates. This allows the satellite platform to take sharp images immediately upon slewing to the target without the need for complex and relatively slow attitude stabilization systems.

The direct detection and characterization of an Earth-like exoplanet is of the highest scientific priority and a leading technology that will enable such discovery is the starshade external occulter. We report on the latest results in ground-based efforts for demonstrating and advancing the technology of starshades. Using the McMath- Pierce Solar Telescope at the Kitt Peak National Observatory, we are able to track stars as they move across the night sky and stabilize a beam of starlight behind a starshade. This has allowed us to conduct the first astronomical observations achieving high-contrast with starshades. In our latest efforts, we have extended the separation between the starshade and telescope to reach an inner working angle of 10 arcseconds at a flight-like Fresnel number and resolution. In this report, we detail the development of a closed-loop feedback system to further stabilize the beam at the extended baseline and provide results on the contrast achieved. We conclude by laying out future work to design a dedicated siderostat-starshade facility for future testing of and observations with starshades. Our main result: we achieved a broadband contrast ratio of 3:2 x 10-5 at 15 arcseconds IWA, while at a flight-like Fresnel number and resolution.

The EUSO (Extreme Universe Space Observatory) project is developing a new mission concept for the scientific research of Ultra High Energy Cosmic Rays (UHECRs) from space. The EUSO wide-field telescope will look down from space onto the Earth night sky to detect UV photons emitted from air showers generated by UHECRs in our atmosphere. In this article we concentrate on the mitigation strategies agreed so far, and in particular on the implementation of a careful early selection and testing of subsystem materials (including optics), design and interfaces of the subsystem and an optimization of the instrument operational concept., Comment: Proceedings of the SPIE, 2016, Paper No. 9983-50

To optimize the observing strategy of a large survey such as the LSST, one needs an accurate model of the night sky emission spectrum across a range of atmospheric conditions and from the near-UV to the near-IR. We have used the ESO SkyCalc Sky Model Calculator 1, 2 to construct a library of template spectra for the Chilean night sky. The ESO model includes emission from the upper and lower atmosphere, scattered starlight, scattered moonlight, and zodiacal light. We have then extended the ESO templates with an empirical fit to the twilight sky emission as measured by a Canon all-sky camera installed at the LSST site. With the ESO templates and our twilight model we can quickly interpolate to any arbitrary sky position and date and return the full sky spectrum or surface brightness magnitudes in the LSST filter system. Comparing our model to all-sky observations, we find typical residual RMS values of ±0.2-0.3 magnitudes per square arcsecond.

With 18 telescopes distributed over 6 sites, and more telescopes being added in 2016, Las Cumbres Observatory Global Telescope Network is a unique resource for timedomain astronomy. The Network's continuous coverage of the night sky, and the optimization of the observing schedule over all sites simultaneously, have enabled LCOGTusers to produce significant science results. However, practical challenges to maximizing the Network's science output remain. The Network began providing observations for members of its Science Collaboration and other partners in May 2014. In the two years since then, LCOGT has made a number of improvements to increase the Network's science yield. We also now have two years' experience monitoring observatory performance; effective monitoring of an observatory that spans the globe is a complex enterprise. Here, we describe some of LCOGT's efforts to monitor the Network, assess the quality of science data, and improve communication with our users.

A novel approach is used to characterize and compare the performance of night vision systems in conditions more representative of night operation in terms of spectral content. Its main advantage compared to standard testing methodologies is that it provides a fast and efficient way for untrained observers to compare night vision system performances with realistic illumination spectra. The testing methodology relies on a custom tumbling-E target and on a new LED-based illumination source that better emulates night sky spectral irradiances from deep overcast starlight to quarter-moon conditions. In this paper, we describe the setup and we demonstrate that the novel approach can be an efficient method to characterize among others night vision goggles (NVG) performances with a small error on the photogenerated electrons compared to the STANAG 4351 procedure.

The Pi of the Sky is a system of five autonomous detectors designed for continuous observation of the night sky, mainly looking for optical flashes of astrophysical origin, in particular for Gamma Ray Bursts (GRB). In the Pi of the Sky project we also study many kinds of variable stars (periods in range of 0.5d - 1000.0d) or take part in the multiwavelength observing campaigns, such as the DG Cvn outburst observations. Our wide field of view robotic telescopes are located in San Pedro the Atacama Observatory, Chile and INTA El Arenosillo Observatory, Spain and were designed for monitoring a large fraction of the sky with 12m -13m range and time resolution of the order of 1 - 10 seconds. During analysis of the variable stars observations very important is accurate determination of their variability parameters. We know a lot of algorithms which can be used to the variability analysis of the observed stars123 . In this article using Monte Carlo analysis we compare all used by us the period detection algorithms dedicated to the astronomical origin data analysis. Based on the tests performed we show which algorithm gives us the best period detection quality and try to derived approximate formula describing the period detection error. We also give some examples of this calculation based on the observed by our detectors variable stars. At the end of this article we show how removing bad measurements from the analysed light curve affect to the accuracy of the period detection.

Retrieval errors of the atmospheric composition using optical methods (DOAS et al.) are under the determining influence of the cloudiness during the measurements. If there is information about the clouds, the optical model of the atmosphere used to interpret the measurements can be adjusted, and the retrieval errors are reduced. For the reconstruction of the parameters of clouds a method was developed based on taking pictures of the sky by a pair of digital photocameras and subsequent processing of the obtained sequence of stereo frames by a method of morphological analysis of images. Since the directions of the optical axes of the cameras are not exactly known, the calibration of the direction of sight of the cameras was conducted at the first stage using the photographs of the stars in the night sky. At the second stage, the relative shift of the image of the cloud fragment on the second frame of the pair was calculated. Stereo pairs obtained by simultaneous photography, allowed us to estimate the height of cloud. The report describes a mathematical model of measurement, pose and solve the problem of calibration of direction of sight of the cameras, describes methods of combining of image fragments by morphological method, the problem of estimating cloud height and speed of their movement is formulated and solved. The examples of evaluations in a real photo are analyzed and validated by the way of comparing with the results of measurement by laser rangefinder.

Twilight/night sky images are often used for flat-fielding CCD images, but the brightness gradient in twilight/night sky causes problems of accurate flat-field correction in astronomical images for wide-field telescopes. Using data from the Antarctic Survey Telescope (AST3), we found that when the sky brightness gradient is minimum and stable, there is still a gradient of 1% across AST3's field-of-view of 4.3 square degrees. We tested various approaches to remove the varying gradients in individual flat-field images. Our final optimal method can reduce the spatially dependent errors caused by the gradient to the negligible level. We also suggest a guideline of flat-fielding using twilight/night sky images for wide-field robotic autonomous telescopes., 7 pages, 5 figures, Proc. SPIE 9149 (2014)

The world at night offers a wealth of stimuli and opportunities as a resource for Optics education, at all age levels and from any (formal, non formal or informal) perspective. The starry sky and the urban nightscape provide a unique combination of pointlike sources with extremely different emission spectra and brightness levels on a generally darker, locally homogeneous background. This fact, combined with the particular characteristics of the human visual system under mesopic and scotopic conditions, provides a perfect setting for experiencing first-hand different optical phenomena of increasing levels of complexity: from the eye's point spread function to the luminance contrast threshold for source detection, from basic diffraction patterns to the intricate irradiance fluctuations due to atmospheric turbulence. Looking at the nightscape is also a perfect occasion to raise awareness on the increasing levels of light pollution associated to the misuse of public and private artificial light at night, to promote a sustainable use of lighting, and to take part in worldwide citizen science campaigns. Last but not least, night sky observing activities can be planned and developed following a very flexible schedule, allowing individual students to carry them out from home and sharing the results in the classroom as well as organizing social events and night star parties with the active engagement of families and groups of the local community. This contribution describes these possibilities and introduces some of the free resources available to put them in practice.

We study the effects of atmospheric emission lines in the night sky on spectroscopic measurements in the 0.4-2.4 μm range at resolutions 100≤R≤50000 to determine an optimal observing resolution. We build a model of the background sky spectrum at various moon phases and calculate the fraction of pixels free of emission lines in 7 different band passes while varying the resolution. We then discuss the effect of the background emission on the signal-to-noise of constant flux targets to determine an optimal resolution at which to observe. Preliminary results show that the emission lines have little to no effect on the selection of resolution in the optical, but that in the wavelengths ranging from 1.0-2.4 μm the effects of atmospheric emission line suggests observing at a resolution of R>2000 is recommended.

Thirty micron has remained one of unexplored frontiers of ground-based astronomical observations. Recent developments of extreme high sites including the Chajnantor TAO site (5,640m) enable us to access the this wavelengths from the ground. The expected transmittance seems clear enough for astronomical observations, but practical evaluations based on astronomical data has not been carried out yet. We have analyzed images obtained at the 31.7 micron with a mid-infrared camera MAX38 attached on a mini-TAO 1.0-meter telescope. 109 images of a star IRC+10420 and 11,114 images of the sky have been reduced. Clear relationship between the measured photocurrents and the perceptible water vapor has been found. Simple estimation of the photocurrents with of the ATRAN model gives good agreements with the measurements, indicating that the ATRAN model reproduce the atmospheric transmittance reasonably well. This also supports our assumption that the scaling factor 0.85 of the PVW at the Chajnantor TAO site to the PWV at the APEX. The average transmittance in the 31.7 micron is achieved to be over 20% when the PWV below 0.6 mm. In some cases clear degradation up to 10% in the transmittance is found. It may be caused by droplets of liquid or iced water with a size over 10 micron although the causes are not exactly specified. Diurnal time variations of the sky photocurrents are also investigated. The sky is sometimes bright and usually unstable in the twilight time. On the other hand the sky around the noontime does not show clear difference from the night sky. It may suggest that the observing condition at the thirty micron windows remain good even in the daytime.

As part of the image quality (IQ) assessment and improvement initiative being carried out at the 3.6m Canada France Hawaii Telescope (CFHT) on Mauna Kea, Hawaii, our objective in the work reported here is to obtain a systematic assay of thermal sources within the dome and in the summit environment around the observatory, and therefore mitigate their contributions to convective instability leading to 'dome seeing'. Toward this, we undertook a nighttime overflight to capture thermal images with a calibrated infrared camera of the outer structures of CFHT and the neighboring observatories on the summit ridge, as well as of a significant area of the surrounding terrain. The same thermal camera was then used to image heat sources within the dome. Using a convective heat transfer model, all these measured surface temperatures were converted to heat fluxes, and thus used to build a thermal assay of the dome. In addition, using button type temperature loggers, we simultaneously recorded the nighttime dome skin temperatures of CFHT and two other observatories over a weeklong period to evaluate nighttime supercooling of the dome skin due to radiation to the cold night sky. As a complementary goal we compared the efficacy of different paints and coatings used in observatories to minimize this effect. Though similar studies have been carried out at other observatories, the results are rarely available in published literature. Therefore, here we explain our methodologies, along with a detailed discussion of our results and inferences to serve as a useful resource to the larger observing community.

We describe here a multiband all sky monitoring system under construction using amateur resources. The system consists of a data management center and a network of telescopes. The total number of telescopes in this network can be huge and all the telescopes are not affected by their local weather or their operability so this network is capable of monitoring the whole night sky simultaneously in many different bands. The telescopes in the network can be operated on an individual basis or on a coordinated mode. The data taken by the telescopes in the network are sent to the data management center via internet where calibration, data fusion, data analysis are performed.

Star cameras represent a well-known class of attitude determination sensors. At this time, they achieve excellent accuracy within arc-seconds. However their size, mass, power, and cost make current commercial versions unacceptable for use on nano-satellites. Here, the concept of developing a small star camera with very modest accuracy requirements for future nano-satellite missions is studied. A small commercial cmos sensor with minimal commercial optics is presented. The cmos imager has an active array area of 5.7 × 4.3mm, with a focal length of 6mm and an aperture ratio of 1.4. This camera's field-of-view is approximately 50 × 40 degrees and can capture stars of magnitudes smaller than 3 with acquisition times of 100ms. The accuracy of attitude determination methods using data collected by this camera was tested by taking photos of the night sky under terrestrial conditions. The camera attitude was determined using offline image processing and star field attitude determination algorithms. Preliminary attitude accuracy results were determined and they are presented.

It is well known that luminance from photo-chemical reactions of hydroxyl ions in the upper atmosphere (~85 km altitude) produces a significant amount of night time radiation in the short wave infra-red (SWIR) band of wave length 0.9 to 1.7 μm. Numerous studies of these phenomena have demonstrated that the irradiance shows significant temporal and spatial variations in the night sky. Changes in weather patterns, seasons, sun angle, moonlight, etc have the propensity to alter the SWIR air glow irradiance pattern. By performing multiple SWIR measurements a mosaic representation of the celestial hemisphere was constructed and used to investigate these variations over time and space. The experimental setup consisted of two sensors, an InGaAs SWIR detector and a visible astronomical camera, co-located and bore sighted on an AZ-EL gimbal. This gimbal was programmed to view most of the sky using forty five discrete azimuth and elevation locations. The dwell time at each location was 30 seconds with a total cycle time of less than 30 minutes. The visible astronomical camera collected image data simultaneous with the SWIR camera in order to distinguish SWIR patterns from clouds. Data was reduced through batch processing producing polar representations of the sky irradiance as a function of azimuth, elevation, and time. These spatiotemporal variations in the irradiance, both short and long term, can be used to validate and calibrate physical models of atmospheric chemistry and turbulence. In this paper we describe our experimental setup and present some results of our measurements made over several months in a rural marine environment on the Island of Kauai Hawaii.

It is well known that luminance from photo-chemical reactions of hydroxyl ions in the upper atmosphere (~85 km altitude) produces a significant amount of night time radiation in the short wave infra-red (SWIR) band of wave length 0.9 to 1.7 μm. Numerous studies of these phenomena have demonstrated that the irradiance shows significant temporal and spatial variations in the night sky. Changes in weather patterns, seasons, sun angle, moonlight, etc have the propensity to alter the SWIR air glow irradiance pattern. By performing multiple SWIR measurements a mosaic representation of the celestial hemisphere was constructed and used to investigate these variations over time and space. The experimental setup consisted of two sensors, an InGaAs SWIR detector and a visible astronomical camera, co-located and bore sighted on an AZ-EL gimbal. This gimbal was programmed to view most of the sky using forty five discrete azimuth and elevation locations. The dwell time at each location was 30 seconds with a total cycle time of less than 30 minutes. The visible astronomical camera collected image data simultaneous with the SWIR camera in order to distinguish SWIR patterns from clouds. Data was reduced through batch processing producing polar representations of the sky irradiance as a function of azimuth, elevation, and time. These spatiotemporal variations in the irradiance, both short and long term, can be used to validate and calibrate physical models of atmospheric chemistry and turbulence. In this paper we describe our experimental setup and present some results of our measurements made over several months in a rural marine environment on the Islands of Kauai and Maui Hawaii.

Since March 2005 Gemini North Observatory routinely propagates a 12W solid state sodium laser into the night sky as part of Adaptive Optics imaging on dimmer portions of the celestial sphere. Gemini along with Keck and Subaru telescopes have created aircraft spotting programs to meet the FAA's rules for aircraft avoidance for outdoor laser propagation. This paper reviews the GN laser safety protocol for the outdoor use of lasers and assessment of the risks considered as part of outdoor laser propagation. We will show the results of Gemini's Aircraft Spotter program, and its continuous development over the past 5 years. As part of a continuous improvement activity Gemini in conjunction with the other laser equipped MK Observatories, Keck and Subaru, is currently testing the use of an all sky camera (ASCAM) to monitor the night sky and shutter the laser for air traffic over the Mauna Kea summit, HI. Use of the ASCAM is expected to increase the efficiency and accuracy of the aircraft spotting program. Gemini not only complies with, but strives to exceed the strict FAA rules for aircraft avoidance for outdoor laser propagation. The creation and implementation of the ASCAM is reviewed in this paper.

A novel radiometric all-sky infrared camera [RASICAM] has been constructed to allow automated real-time quantitative assessment of night sky conditions for the Dark Energy Camera [DECam] located on the Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile. The camera is optimized to detect the position, motion and optical depth of thin, high (8-10km) cirrus clouds and contrails by measuring their apparent temperature above the night sky background. The camera system utilizes a novel wide-field equiresolution catadioptic mirror system that provides sky coverage of 2π azimuth and 14-90° from zenith. Several new technological and design innovations allow the RASICAM system to provide unprecedented cloud detection and IR-based photometricity quantification. The design of the RASICAM system is presented.

We describe the design and operation of a small, transportable, robotic observatory that has been developed at Los Alamos National Laboratory. This small observatory, called RQD2 (Raptor-Q Design 2), is the prototype for nodes in a global network capable of continuous persistent monitoring of the night sky. The observatory employs five wide-field imagers that altogether view about 90% of the sky above 12 degrees elevation with a sensitivity of R=10 magnitude in 10 seconds. Operating robotically, the RQD2 system acquires a nearly full-sky image every 20 seconds, taking more than 10,000 individual images per night. It also runs real-time astrometric and photometric pipelines that provide both a capability to autonomously search for bright astronomical transients and monitor the variability of optical extinction across the full sky. The first RQD2 observatory began operation in March 2009 and is currently operating at the Fenton Hill site located near Los Alamos, NM.We present a detailed description of the RQD2 system and the data taken during the first several months of operation.

Nigel is a fiber-fed UV/visible grating spectrograph with a thermoelectrically-cooled 256×1024 pixel CCD camera, designed to measure the twilight and night sky brightness from 300nm to 850 nm. Nigel has three pairs of fibers, each with a field-of-view with an angular diameter of 25 degrees, pointing in three fixed positions towards the sky. The bare fibers are exposed to the sky with no additional optics. The instrument was deployed at Dome A, Antarctica in January 2009 as part of the PLATO (PLATeau Observatory) robotic observatory. During the 2009 winter, Nigel made approximately six months of continuous observations of the sky, with typically 104 deadtime between exposures. The resulting spectra provide quantitative information on the sky brightness, the auroral contribution, and the water vapour content of the atmosphere. We present details of the design, construction and calibration of the Nigel spectrometer, as well some sample spectra from a preliminary analysis.

Low-light level night vision device must be assessed by light stress reliability test in the design approval testing and production approval testing. The low-light level stress environment is the key to light stress reliability test on Low-light level night vision device. This paper studies the actual working environment of Low-light level night vision device from the aspects of night sky spectrum of nature light and illumination, and designs a low-light level stress system. The system consists of double-integrating-sphere light source, light stress automatic switching device, collimator, monitoring and control system for light stress. The system uses a total light source with radiation structure to improve the light efficiency, solve the question of light stress consistency, achieve a typical night-day simulation of the environment and the monitoring and control of the whole process.

Visible-band cameras using silicon imagers provide excellent video under daylight conditions, but become blind at night. The night sky provides illumination from 1-2 μm which cannot be detected with a silicon sensor. Adding short-wave infrared detectors to a CMOS imager would enable a camera which can be used day or night. A germanium-enhanced CMOS imager (TriWave®) has been developed with broadband sensitivity from 0.4 μm to 1.6 μm. A 744 x 576 format imager with 10 μm pixel pitch provides a large field of view without incurring a size and weight penalty in the optics. The small pixel size is achieved by integrating a germanium photodetector into a mainstream CMOS process. A sensitive analog signal chain provides a noise floor of 5 electrons. The imagers are hermetically packaged with a thermo-electric cooler in a windowed metal package 5 cm3 in volume. A compact (

A typical configuration of attitude estimation system for a spacecraft consists of multiple star trackers, coupled with gyroscopes and coarse sensors such as Sun or Earth sensors. The combination of these sensors results in high mass, volume and power requirements. StarVision has been actively developing an unique sensor that is capable of providing attitude and angular rate information from star measurements at update rates of 100Hz. The SG100 stellar gyroscope is built around an image intensified imaging core that is sensitive to stars as faint as visual magnitude 10 at very small exposure times. In this paper we report the development of the SG100 sensor. Results from sensitivity analysis as well as night sky tests at angular rates as high as 20deg/s will be presented. Test data shows that the SG100 far exceeds the requirements of star sensitivity and noise levels even under non-ideal imaging conditions.

A thermal model of the Discovery Channel Telescope (DCT) was used to estimate the contribution of major sources of local seeing; shell seeing, dome seeing and mirror seeing. The model simulates a dynamic equilibrium over several day/night cycles taking into account the morphology of the facility, diurnal insolation and radiation to the night sky, local air temperature and humidity swings, wind and air flow through the facility, and infiltration from warm spaces within the facility. The model confirmed that the well ventilated design of the DCT facility will virtually eliminate dome seeing, but that shell seeing and mirror seeing could be major contributors to local seeing. These can be mitigated by the choice of an appropriate exterior coating, and by cooling the primary mirror.

An inexpensive solution using an artificial vision system appears to the problem of pointing, tracking and guiding a telescope. A stellar sensor called "R2D2" has been developed. The elements of the system are a CMOS sensor with the respective optics and "Oeil 1.0", a software package that we have developed under the object oriented environment of Matlab 7.0. The software is built in a graphical user interface that allows an easy interaction between the user and the system. The stellar sensor is mounted in parallel to the telescope, captures images of the night sky and sends them to the software, which makes preprocessing and noise reduction routines, identifies the stars and their centroids, and calculates the equatorial coordinates of all the stars, the center of the image and any other point into the image. Finally the tracking of the stellar object placed in the center of the field of view is made thanks to the continuously feedback of images and the successful results obtained with the image processing techniques.

We present a novel design of an all-sky 4096 × 4096 pixels camera devoted to continuous observations of the sky.A prototype camera is running at the BOOTES-1 astron omical station in Huelva (Spain) since December 2002and a second one is working at the BOOTES-2 station in M´ alaga (Spain) since July 2004. Scienti“c applicationsare the search for simultaneous optical emission associated to gamma-ray bursts, study of meteor showers, anddetermination of possible areas for meteorite recovery fr om the reconstruction of “reball trajectories. This lastapplication requires that at least two such devices for simultaneously recording the sky at distance of the orderof 100 km. Fifteen GRB error boxes (13 for long/soft events and 2 for short/hard GRBs) have been imagedsimultaneously to the gamma-ray emission, but no opti cal emission has been detected. Bright “reballs have beenalso recorded, allowing the determination of trajectories, as in the case of the “reball of 30 July 2005. This deviceis a very promising instrument for continuous recording of the night sky with moderate angular resolution andlimiting magnitude (up to R 10).

To study space attack-defense technology, a simulation of satellites is needed. We design and implement a 3d simulating system of satellites. The satellites are rendered under the Night sky background. The system structure is as follows: one computer is used to simulate the orbital of satellites, the other computers are used to render 3d simulation scene. To get a realistic effect, a three-channel multi-projector display system is constructed. We use MultiGen Creator to construct satellite and star models. We use MultiGen Distributed Vega to render the three-channel scene. There are one master and three slaves. The master controls the three slaves to render three channels separately. To get satellites' positions and attitudes, the master communicates with the satellite orbit simulator based on TCP/IP protocol. Then it calculates the observer's position, the satellites' position, the moon's and the sun's position and transmits the data to the slaves. To get a smooth orbit of target satellites, an orbit prediction method is used. Because the target satellite data packets and the attack satellite data packets cannot keep synchronization in the network, a target satellite dithering phenomenon will occur when the scene is rendered. To resolve this problem, an anti-dithering algorithm is designed. To render Night sky background, a file which stores stars' position and brightness data is used. According to the brightness of each star, the stars are classified into different magnitude. The star model is scaled according to the magnitude. All the stars are distributed on a celestial sphere. Experiments show, the whole system can run correctly, and the frame rate can reach 30Hz. The system can be used in a space attack-defense simulation field.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A robotic system for continuous observation of a night sky is proposed. The "Full Pi of the Sky" system will consist of 32 CCD cameras and 8 motorized parallaactic mounts. The location of a future observation site requires full remote control and autonomous on-line and off-line data analysis. Inorder to test scalability of the sytem and to develop optimal control and analysis algorithms a full, real-time jardware simulation will be employed. The concept of the "Full Pi of the Sky" architecture and some aspects of its software emulation are discussed in this paper.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The brightness of the night sky at an astronomical site is one of the principal factors that determine the quality of available optical observing time. At any site the optical night sky is always brightened with airglow, zodiacal light, integrated starlight, diffuse Galactic light and extra-galactic light. Further brightening can be caused by scattered sunlight, aurorae, moonlight and artificial sources. Dome C exhibits many characteristics that are extremely favourable to optical and IR astronomy; however, at this stage few measurements have been made of the brightness of the optical night sky. Nigel is a fibre-fed UV/visible grating spectrograph with a thermoelectrically cooled 256 × 1024 pixel CCD camera, and is designed to measure the twilight and night sky brightness at Dome C from 250 nm to 900 nm. We present details of the design, calibration and installation of Nigel in the AASTINO laboratory at Dome C, together with a summary of the known properties of the Dome C sky.

The All-Sky camera used in the LSST and TMT site testing campaigns is described and some early results are shown. The All-Sky camera takes images of the entire visible hemisphere of sky every 30s in blue, red, Y and Z filters giving enhanced contrast for the detection of clouds, airglow and the near-infrared. Animation is used to show movement of clouds. An additional narrow band filter is centered on the most prominent line of the sodium vapor lamp spectra and is used to monitor any man-made light pollution near the site. The camera also detects aircraft lights and contrails, satellites, meteor(ite)s, local light polluters, and can be used for stellar extinction monitoring and for photometry of transient astronomical objects. For outreach and education the All-Sky camera can show wandering planets, diurnal rotation of the sky, the zodiacal light, and similar astronomical basics.

CMOS APS based star tracker is a new generation of attitude sensor. An APS based autonomous star tracker has been proposed. This paper gives a primary demonstration of the software performance of the proposed star tracker, through laboratory and real night sky experiments. The star pattern recognition algorithm in the software protocol uses a quick search and robust match strategy and can perform independent star identification without prior attitude knowledge. The laboratory experiments validated the whole sky independent star pattern recognition algorithm and showed a comprehensive influence of errors and noise on the software performance. The real night sky experiments tested the sensitivity of the APS star sensor and validated the feasibility of the star identification and attitude estimation algorithm. In this paper, the structure and procedure of the software is described. The experiment system setup is introduced and the results of the laboratory and real sky experiments are presented and discussed.

The UKIRT Wide Field Camera (WFCAM) on Mauna Kea and the VISTA IR mosaic camera at ESO, Paranal, with respectively 4 Rockwell 2kx2k and 16 Raytheon 2kx2k IR arrays on 4m-class telescopes, represent an enormous leap in deep IR survey capability. With combined nightly data-rates of typically 1TB, automated pipeline processing and data management requirements are paramount. Pipeline processing of IR data is far more technically challenging than for optical data. IR detectors are inherently more unstable, while the sky emission is over 100 times brighter than most objects of interest, and varies in a complex spatial and temporal manner. In this presentation we describe the pipeline architecture being developed to deal with the IR imaging data from WFCAM and VISTA, and discuss the primary issues involved in an end-to-end system capable of: robustly removing instrument and night sky signatures; monitoring data quality and system integrity; providing astrometric and photometric calibration; and generating photon noise-limited images and astronomical catalogues. Accompanying papers by Emerson etal and Hambly etal provide an overview of the project and a detailed description of the science archive aspects.

The results of the hydroxyl and oxygen molecules rotational temperature measured during two observational seasons 1999-2001 and Maymaga station (φ=63°N; λ=129.50°E) are presented. It is shown that the amplitude of seasonal variation of hydroxyl rotational temperature is greater than the molecular oxygen variation. OH temperatures have been systematically higher the O2 ones during winter. The abrupt decreasing of the O2 intensity connected with the springtime transition of the atmospheric circulation process is found in both time series. In first time a change of the temperature vertical gradient sign caused by the mesopause height shifting to the more high ( winter) level was shown in the data of August-September 2001. Comparisons of night airglow variations with stratospheric temperature over Yakutsk at the 10 mb height, averaged over the polar cap (latitudes of ≥65°N), is presented. The waves registered in mesosphere by variation of molecular oxygen emission rate are of periods up to ten days, and the envelope of their amplitudes is similar to stratosphere temperature oscillations with a time scale of approximately 30 days. Such a close association of two different parameters in the atmosphere regions separated in height can be explained by passage of large-scale wave disturbances through them.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.