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1.
Based on the measurements performed from 2007 to 2015 at the summit of Mount Shatdzhatmaz adjacent to the 2.5-m telescope at the Caucasus Observatory of the SAI MSU, we have determined the statistical characteristics of basic meteorological parameters: the ambient air temperature, the ground wind speed, and the relative humidity. The stability of these parameters over the entire period of our measurements and their variations within an annual cycle have been studied. The median temperature on clear nights is +3.2°C, although there are nights with a temperature below ?15°C. The typical ground wind speed is 3 m s?1; the probability of a wind stronger than 10 m s?1 does not exceed 2%. The losses of observing time due to high humidity are maximal in the summer period but, on the whole, are small over a year, less than 10%. We have estimated the absolute water vapor content in the atmosphere, which is especially important for infrared observations. Minimum precipitablewater vapor is observed in December–February; the median value over these months is 5 mm. We additionally provide the wind speeds at various altitudes above the ground (from 1 to 16 km) that we obtained when measuring the optical turbulence. We present the results and technique of our measurements of the annual amount of clear night astronomical time, which is, on average, 1320 h, i.e., 45% of the possible one at the latitude of the observatory. The period from mid-September to mid-March accounts for about 70% of the clear time. A maximum of clear skies is observed in November, when its fraction reaches 60% of the possible astronomical night time.  相似文献   

2.
Fabry-Perot interferometer measurements of Doppler shifts and widths of the 630.0 nm nightglow line have been used to determine the neutral winds and temperatures in the equatorial thermosphere over Natal, Brazil during August–September 1982. During this period, in the early night (2130 U.T.) the average value of the horizontal wind vector was 95 m s?1 at 100° azimuth, and the temperature varied from a low of 950 K during geomagnetically quiet conditions to a high of ~ 1400 K during a storm (6 September). The meridional winds were small, ?, 50 m s?1, and the eastward zonal winds reached a maximum value 1–3 h after sunset, in qualitative agreement with TGCM predictions. On 26 August, an observed persistent convergence in the horizontal meridional flow was accompanied by a downward vertical velocity and an increase in the thermospheric temperature measured overhead. Oscillations with periods of 40–45 min in both the zonal and vertical wind velocities were observed during the geomagnetic storm of 6 September, suggesting gravity wave modulation of the equatorial thermospheric flow.  相似文献   

3.
The paper presents a study of large scale travelling ionospheric disturbances detected by riometers operating at 30 MHz, over São José dos Campos (23°S, 45°W) and a nearby location in Sao Paulo, Brasil. The TID's are observed mainly at night and have wavelengths greater than 500 Km. In a few cases it is possible to determine the E-W component of the velocity of propagation, which is of the order of 450 Km per hour. Most of the events are characterized by disperions; the period is found to increase from half an hour to nearly two hours. These and other features are identified with the propagation of atmospheric gravity waves in the F-region, whose source might be located far away from the observing site. The results also suggest that a suitably designed riometer system could profitably be used for future investigation of gravity waves in the F-region in low latitude.  相似文献   

4.
A series of simultaneous incoherent-backscatter and 6300 Å tilting-filter photometer observations were made in the winter and early spring of 1972 at Chatanika, Alaska. These observations have been combined for magnetically quiet nights to deduce the presence of excitation by two sources in addition to dissociative recombination. The first appears to be a source that is steady for at least three hours, centered about local midnight, but that varies from night to night, taking on values between 10 and 40 Rayleighs for the nights in question. It is suggested that this source may be a flux of low-energy electrons or protons. The second source is impact excitation by electrons from the magnetic conjugate point. The emission due to this source appears to be small immediately after local sunset, rises to a maximum at about 92° conjugate solar zenith angle (CSZA), and then decreases to zero in the vicinity of 105° CSZA. The deduced intensities for this source at 92° CSZA are in the region of 15–30 Rayleighs for local F-layer critical frequencies of 3?2 MHz, respectively.  相似文献   

5.
The emission of the upper atmosphere introduces an additional variable component into observations of astronomical objects in the NIR 700–3,000 nm range. The subtraction of this component is not easy because it varies during the night by as much as 100% and it is not homogeneous over the sky. A program aimed at measuring and understanding the main characteristics of the atmospheric NIR emission was undertaken. A 512?×?512 CCD camera equipped with a RG780/2 mm filter is used to obtain images of the sky in a 36°?×?36° field of view. The intensities of a given star and of the nearby region devoid of star in a 439 arcmin2 area are monitored during periods of time of several hours. The sky intensity measured in the 754–900 nm bandpass, reduced to zenith and zero airmass is comprised between mag20 and mag18.5 per arcsecond2. A diminution by a factor of two during the night is frequently observed. Intensity fluctuations having an amplitude of 15% and periods of 5–40 min are present in the images with a structure of regularly spaced stripes. The fluctuations of the NIR sky background intensity are due to (1) the chemical evolution of the upper atmosphere composition during the night and (2) dynamical processes such as tides with periods of 3–6 h or gravity waves with periods of several tens of minutes. We suggest that a monitoring of the sky background intensity could be set up when quantitative observations of astronomical objects require exposure times longer than ~10 min. The publication is illustrated with several video films accessible on the web site http://www.obs-besancon.fr/nirsky/. Enter username: nirsky and password: skynir.  相似文献   

6.
Values of plasma temperature and vertical temperature gradient were obtained by fitting theoretical models to 60,000 observed electron density profiles, at heights of 400–1000 km. Results show the diurnal and seasonal changes in temperature from 75°S to 85°N near solar minimum. At night the temperature and temperature gradient are both low inside the plasmapause and high outside. Day-time temperatures increase almost linearly with latitude, from 1500 K at the magnetic equator to a maximum of 3500 K at the plasmapause. There is also a sharp peak at 77° latitude, beneath the magnetospheric cleft. Mean vertical temperature gradients are ca. 0.5 Kkm at night, and 1–4 K/km during the day. The downwards flow of heat, during the day, increases from about zero at 10° latitude to a maximum of 4 × 109eVcm2sec at the plasmapause. Night-time flows are 5–20 times less, inside the plasmasphere. Increases in magnetic activity cause a temperature increase at 400 km, of about 70 K per unit increase in Kp at all latitudes greater than 65°. The temperature peaks at the plasmapause and the magnetospheric cleft show little increase with magnetic activity, but move equatorwards by ca. 2° in latitude per unit Kp.  相似文献   

7.
The M.F. radar (2.2 MHz) operating at Saskatoon, Canada (52°N, 107°W) has been used to obtain continuous winds data for 1982/3: heights are ～60–110 km in daylight hours and ～80–110 km at night. The monthly data are compared with means of prevailing winds, tides (12-, 24-h) and planetary waves for the previous 4 years: 1978–1982. A regular climatology emerges that strongly suggests that the theoretical modelling of the upper middle atmosphere is an achievable goal: also that updated global data models are required.  相似文献   

8.
An analysis of the Mariner 10 dual frequency radio occultation recordings has yielded new information on the radius and atmosphere of Mercury. The ingress measurements which were conducted near 1.1° North latitude and 67.4° East longitude on the night side of the planet, gave a value for the radius of 2439.5 ± 1 km. Egress near 67.6° North latitide and 258.4° East longitude in the sunlit side yielded a radius of 2439.0 ± 1 km. The atmospheric measurements showed the electron density to be less than 103 cm?3 on both sides of the planet. From the latter result one may infer an upper limit to the dayside surface gas density of 106 molecules per cm3.  相似文献   

9.
The lunar sodium tail extends long distances due to radiation pressure on sodium atoms in the lunar exosphere. Our earlier observations measured the average radial velocity of sodium atoms moving down the lunar tail beyond Earth (i.e., near the anti-lunar point) to be ～12.5 km/s. Here we use the Wisconsin H-alpha Mapper to obtain the first kinematically resolved maps of the intensity and velocity distribution of this emission over a 15° × 15 ° region on the sky near the anti-lunar point. We present both spatially and spectrally resolved observations obtained over four nights bracketing new Moon in October 2007. The spatial distribution of the sodium atoms is elongated along the ecliptic with the location of the peak intensity drifting 3° east along the ecliptic per night. Preliminary modeling results suggest the spatial and velocity distributions in the sodium exotail are sensitive to the near surface lunar sodium velocity distribution. Future observations of this sort along with detailed modeling offer new opportunities to describe the time history of lunar surface sputtering over several days.  相似文献   

10.
Photoelectric measurements have been carried out at Kottamia Observatory site to study night sky brightness and the atmospheric extinction at different wavelengths. The results show that the mean extinction coefficients are k = 0.41, k = 0.28< and k = 0.17 mag/air mass during autumn season. These values are almost the same as that obtained by Mikhail (1979) at the same site during the same season. Results of night sky brightness at different altitudes above the horizon have been obtained. Complete scan each five degrees step in azimuth have been done at altitudes 50°, 60° and 70° to complete the previous measurements given by Nawar et al. (1995). Far from the diffuse galactic light, slight variations in night sky brightness with azimuth have been detected. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

11.
We report the results of position, photometric, and polarimetric observations of two near-Earth asteroids made with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. 1.2-hour measurements of the photometric variations of the asteroid 2009 DL46 made onMarch 8, 2016 (approximately 20m at a distance of about 0.23 AU from the Earth) showed a 0.m2-amplitude flash with a duration of about 20 minutes. During this time the polarization degree increased from the average level of 2–3% to 14%. The angle of the polarization plane and the phase angle were equal to 113° ± 1° and 43°, respectively. Our result indicates that the surface of the rotating asteroid (the rotation period of about 2.5 hours) must be non-uniformly rough. Observations of another asteroid—1994 UG—whose brightness was of about 17m and which was located at a geocentric distance of 0.077 AU, were carried out during the night of March 6/7, 2016 in two modes: photometric and spectropolarimetric. According to the results of photometric observations in Johnson’s B-, V-, and R-band filters, over one hour the brightness of the asteroid remained unchanged within the measurement errors (about 0.m02). Spectropolarimetric observations in the 420–800 nm wavelength interval showed the polarization degree to decrease from 8% in the blue part of the spectrum to 2% in the red part with the phase angle equal to 44?, which is typical for S-type near-Earth asteroids.  相似文献   

12.
Photoelectric observations of night sky brightness at different zenith distances in blue, yellow and red colours have been carried out at Abu-Simbel site. Variations in the night sky brightness and (B-V) colour index with time are detected. These variations have been explained by the change of the galactic latitude of the observed point with time. The deduced results of night sky brightness have been compared with that obtained before at other sites. It has been found for both blue and yellow colours, that Abu-Simbel is the darkest site especially for zenith distances equal or greater than 60°. The present values of night sky brightness and colour have been obtained for the first time at Abu-Simbel site. The average night sky brightness at the galactic plane is 22.58 mag/arc sec2 for blue and 21.66 mag/arc sec2 for yellow. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

13.
Cosmos 378 rocket, 1970-97B, entered orbit on 17 November 1970, with orbital inclination 74.0°, period 105 min and perigee height 230 km, and decayed on 30 September 1972 after 683 days in orbit. The RAE computer program PROP was used, with more than 1900 observations from 64 stations, to determine the orbit at 39 epochs between February 1971 and September 1972.The main aim of the analysis was to determine the atmospheric rotation rate from the decrease in orbital inclination, which was determined with a mean standard deviation of 0.0010° and a best standard deviation of 0.0003°. After removal of relevant perturbations, analysis of the variation in inclination between July 1971 and April 1972 yields the surprisingly low average atmospheric rotation rate of 0.75 ± 0.05 rev/day, at a mean height of 250 km. The local time at perigee is however strongly biassed towards daytime values (07–16 hr), so the results lend support to the picture of east-to-west winds by day and west-to-east winds by night.Values of scale height are obtained by analysis of the change in perigee height.  相似文献   

14.
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15.
OH day and night airglow intensity variations were measured with a three-channel balloon-borne i.r. photometer in four separate flights from southern France in June 1970 and June 1971. The nightglow intensity showed a minimum at some time between midnight and 0200 hr local mean time followed by a steady increase until the end of the night. In all four flights a rapid pre-sunrise decrease in intensity was observed at a solar elevation of ?6°. The dayglow intensities increased slowly after sunrise with the emission reaching half its pre-dawn value near a solar elevation of 36°. The morning twilight observations are compared with other observations and with theoretical predictions.  相似文献   

16.
We present the results of 15184 astrometric observations of 322 visual binaries carried out in 2007–2014 at Pulkovo observatory. In 2007, the 26-inch refractor (F = 10413 mm, D = 65 cm) was equipped with the CCD camera FLI ProLine 09000 (FOV 12′ × 12′, 3056 × 3056 pixels, 0.238 arcsec pixel?1). Telescope automation and weather monitoring system installation allowed us to increase the number of observations significantly. Visual binary and multiple systems with an angular distance in the interval 1.?1–78.?6 with 7.?3 on average were included in the observing program. The results were studied in detail for systematic errors using calibration star pairs. There was no detected dependence of errors on temperature, pressure, and hour angle. The dependence of the 26-inch refractor’s scale on temperature was taken into account in calculations. The accuracy of measurement of a single CCD image is in the range of 0.?0005 to 0.?289, 0.?021 on average along both coordinates. Mean errors in annual average values of angular distance and position angle are equal to 0.?005 and 0.°04 respectively. The results are available here http://izmccd.puldb.ru/vds.htmand in the Strasbourg Astronomical Data Center (CDS). In the catalog, the separations and position angles per night of observation and annual average as well as errors for all the values and standard deviations of a single observation are presented. We present the results of comparison of 50 pairs of stars with known orbital solutions with ephemerides.  相似文献   

17.
New data about the top clouds of Venus were obtained during the radiometric experiment on-board the Venera 9 and Venera 10 orbiters. A diurnal component of the ir thermal radiation was determined for the latitude range ?40, +50°. The brightness temperature of radiation referred to the normal was measured; it was 244°K at night and 239°K at the subsolar point for the 7- to 13-, 17- to 30-μm bands. Minimum temperatures correspond to the meridian of local time 16.00h and are 232°K. There is also a zone of lower temperatures in the region of local time 7.5h. Absolute temperatures were measured with an accuracy of ?1.9°+1.2°. Thermal radiation has no distinct latitudinal dependence but has a day-night asymmetry, with the night radiation flux exceeding that on the day side by 17%. The limb-darkening law for thermal radiation is rather complicated, depending on the time of day. There are at least two states of the radiating cloud cover: day and night. The extinction coefficient is close to 0.24 km?1. The analysis shows that the source function of the medium is close to Planck's function. During the day the flux of thermal radiation is assumed to be weakened by an aerosol medium forming by photochemical processes. Comparison of experimental and calculated data yields a particle concentration in the radiating cloud cover of about 95 cm?3. Experimental data and the results of ground-based measurements were used to determine the radiometric albedo of Venus, 0.79?0.01+0.02.  相似文献   

18.
This paper describes a wide-field survey made at 34.5 MHz using GEETEE,1 the low frequency telescope at Gauribidanur (latitude 13°36′12′′N). This telescope was used in the transit mode and by per forming 1-D synthesis along the north-south direction the entire observable sky was mapped in a single day. This minimized the problems that hinder wide-field low-frequency mapping. This survey covers the declination range of-50° to + 70° (- 33° to +61° without aliasing) and the complete 24 hours of right ascension. The synthesized beam has a resolution of 26′ x 42′ sec (δ- 14°. 1). The sensitivity of the survey is 5 Jy/beam (1σ). Special care has been taken to ensure that the antenna responds to all angular scale structures and is suitable for studies of both point sources and extended objects This telescope is jointly operated by the Indian Institute of Astrophysics, Bangalore and the Roman Research Institute, Bangalore.  相似文献   

19.
In recent years, following the Chelyabinsk event of February 15, 2013, the lower size limit for presumably dangerous near-Earth objects has been decreased manyfold (essentially, from 140 m to ~10 m). This has drawn an increased attention to the properties of the population of decameter-sized bodies, in particular, the bodies that approach the Earth from the sunward side (daytime sky). The current paper is concerned with various properties of this population. The properties of the ensemble are analyzed using both observational data from other authors and theoretical estimates obtained by cloning virtual bodies. This question is of great practical importance, as the means for detecting such bodies (for example, the SODA project) need to be developed with consideration for the requirements imposed by the population properties. We have shown that the average rate of entering near-Earth space (NES), i.e., at distances less than ~1 million km from the Earth, for decameter-sized and larger bodies from the daytime sky (elongation values of entry points less than 90°) is approximately 620 objects per year for elongation angles of the detection point <90° and approximately 220 objects per year for elongation angles of the detection point <45°.  相似文献   

20.
The heliocentric orbits of the two STEREO satellites are similar in radius and ecliptic latitude, with separation in longitude increasing by about 45° per year. This arrangement provides a unique opportunity to study the evolution of stream interfaces near 1 AU over time scales of hours to a few days, much less than the period of a Carrington rotation. Assuming nonevolving solar wind sources that corotate with the Sun, we calculated the expected time and longitude of arrival of stream interfaces at the Ahead observatory based on the in situ solar wind speeds measured at the Behind observatory. We find agreement to within 5° between the expected and actual arrival longitude until the spacecraft are separated by more than 20° in heliocentric inertial longitude. This corresponds to about one day between the measurement times. Much larger deviations, up to 25° in longitude, are observed after 20° separation. Some of the deviations can be explained by a latitude difference between the spacecraft, but other deviations most likely result from evolution of the source region. Both remote and in situ measurements show that changes at the source boundary can occur on a time scale much shorter than one solar rotation. In 32 of 41 cases, the interface was observed earlier than expected at STEREO/Ahead.  相似文献   

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