Instituto Nacional De Pesquisas Espaciais Research Articles

UVB direct sun measurements from Brewer spectrophotometer to determine the aerosol optical thickness at several sites

Brewer spectrophotometer makes direct sun (ds) measurements at five wavelengths in the ultraviolet B (UVB) band. In addition to ozone (O 3) and sulfur dioxide (SO 2) atmospheric column values, Brewer ds measurements have been used to measure the aerosol optical thickness (AOT or τ ae) in the UVB. The atmospheric optical thickness ( τ at) is drawn from the Langley method application to ds measurements. Rayleigh, O 3 and SO 2 contributions are subtracted from τ at and AOT is thus obtained. This technique has been used by the Ozone Lab at Instituto Nacional de Pesquisas Espaciais (INPE) for a large number of diversified environments in Brazil such as savanna in the biomass burning season, coastal cities, rural places, and polluted cities including one in Bolivia. Typical AOT values are 0.60±0.44 in savanna, 0.20±0.17 in coastal cities, 0.29±0.21 in rural places, and 0.45±0.30 in polluted cities.

Comparison of gravity wave activity observed by airglow imaging at two different latitudes in Brazil

An all-sky CCD imager for the OH, O 2and OI (557.7 nm) airglow emissions was operated at Cachoeira Paulista (CP), Brazil (23°S,45°W), in collaboration with Utah State University, USA, during the period of 1998–2000. Another all-sky imager, which belongs to the Instituto Nacional de Pesquisas Espaciais, has been operating at São João do Cariri (Cariri), Brazil (7°S,36°W) since October 2000. Dominant gravity wave components were investigated by using the image data from the two sites. Wave characteristics observed at CP (October 1998–September 1999) show horizontal wavelengths of 5– 60 km , periods of 5– 35 min and horizontal phase velocities of 1– 80 m/s . Band-type waves (horizontal wavelengths between 10 and 85 km ) showed a clear seasonal dependency in the horizontal propagation direction, propagating to the southeast in summer and to the northwest in winter. The Cariri data (September 2000–August 2001) showed horizontal wavelengths of 5– 65 km , with periods of 5– 55 min and horizontal phase velocities of 5– 105 m/s , much higher than CP. Band-type waves also exhibited a seasonal dependency in the horizontal propagation direction, propagating to southeast in summer and northeast in winter. The results are interpreted in terms of wind filtering and a non-uniform distribution of the gravity wave sources.

Scientific ballooning in Brazil

We present an overview of the scientific ballooning activities that took place in Brazil over the past 30 years as well as the current ongoing efforts in the area. We also briefly describe the balloon launching facility that exists at the Instituto Nacional de Pesquisas Espaciais (National Institute for Space Research) — INPE. Up to now, over 100 scientific balloon experiments, related to Astrophysics, Aeronomy, and Geophysics were launched from Brazil taking advantage of the country's continental dimensions, a well-defined rain season, and a low population density, which offer excellent conditions for scientific ballooning activities. Balloons with volumes up to 500,000 cubic meters can be launched from INPE's balloon launching base (latitude S 22° 4′ 2″; longitude W 044° 58′ 41″). The availability of good roads and several inland airports in Brazil provides the necessary structure for safe payload retrieval and its rapid return to the balloon base. There are several airports throughout Brazil that can also be used as balloon launching bases, mainly in the country's Eastern region. Overflights of more than 1,000 kilometers are possible and easily attained. Balloon flights ranging from a few hours to long duration flights can be safely verified. The constant climate monitoring through the use of weather satellites information received at INPE provides the necessary data to determine the necessary conditions for a long duration flight. INPE's Center for Weather Forecast and Climate Studies (CPTEC) provides the necessary weather forecast support for launch and payload retrieval.

Plasma immersion ion implantation experiments at the Instituto Nacional de Pesquisas Espaciais (INPE), Brazil

Historical perspective of the development of PIII devices at the Instituto Nacional de Pesquisas Espaciais (INPE) is given, together with the description of the present system under operation and our overall results on this three-dimensional implantation research. Starting with an ignitron switched pulser (1 pulse per 3 min) and an intermittent microwave plasma, we improved our PIII system developing a pulse forming network (PFN) based pulser (20 Hz), 2 years later. We also improved our plasma source towards a DC, highly stable, medium density glow discharge system. A much faster hard tube pulser was recently incorporated to our PIII system (670 Hz) allowing us to achieve good implantation results in different materials. Presently, we are testing a recently purchased RUP-4 commercial pulser to obtain arc prevented, 1.1 kHz, square pulses for new experiments in this active field of PIII research.

Space science education and training in Brazil

With the beginning of space research in Brazil in the early 60's a national commission for space activities was created. This commission took important steps, in parallel, to create a program of education and training activities that was forseen as of critical importance for the maintainance of a desirable to ambitious degree of space activity in the country. Early efforts were, as a first step, in favour of training of Brazilian students in foreign centers of excellence (mostly in the US and Europe), as a means for achieving the potential human resource necessary for eventual development of a national program. Today a large percentage of the needs in the area is met by programs developed inside the country at different institutions, the most notable being the “Instituto Nacional de Pesquisas Espaciais” -INPE (National Institute for Space Research) at São José dos Campos, where post graduate courses and training programs are well established. Under-graduate courses in selected areas are provided at some Universities, notably at the University of São Paulo. A brief description of the existing programs and an evaluation of the results being achieved are presented in this paper.

Increasing concentrations of CO and O3 rising deforestation rates and increasing troposheric carbon monoxide and ozone in Amazonia

Increasing carbon monoxide and ozone concentrations have been observed in the lower troposphere of the Brazilian Amazon region in recent years (1989-1995). Carbon monoxide and ozone have been measured in the region continuously; from observations at a single site and many sporadic field missions, there is a clear indication that the chemical activity in the troposphere is growing, with increasing concentrations especially during the dry season. On the other hand, the most recent deforestation assessment by the Brazilian Government, performed by the Instituto Nacional de Pesquisas Espaciais (INPE) using Landsat data, shows yearly rates rising from the 11,130 km(2) year(-1) minimum of the 1990/91 survey, to 13,786 km(2) year(-1) for the 1991/92 period, and 14,896 km(2) year(-1) for the period 1992/94. It is argued that the increase in deforestation/biomass burning activities in "Amazonia" have produced larger carbon monoxide and ozone concentrations in the lower atmosphere.

The Brazilian scientific satellite

Two scientific satellites are being proposed by the Instituto Nacional de Pesquisas Espaciais (INPE). The first of them is being designed to carry out about ten ionospheric, thermospheric, magnetospheric and astrophysical experiments. Its orbit will be circular, inclined 25° with respect to the equatorial plane and 700 km of altitude. The spacecraft is to be launched by the Brazilian VLS rocket from the Brazilian equatorial launching facility Alcântara. Details on such a satellite program will be given in this presentation. The plans for the second satellite were incomplete by the time that this paper was written, thus it will not be focused upon here.

Ozone budget over the Amazon: Regional effects from biomass‐burning emissions

A one‐dimensional, time‐dependent, photochemical model is used in conjunction with data obtained during the dry‐season portion of NASA's Global Tropospheric Experiment and Brazil's Instituto Nacional de Pesquisas Espaciais (INPE) (National Institute for Space Research) Amazon Boundary Layer Experiment (ABLE 2A) to simulate the chemistry of the dry‐season Amazon troposphere. The background atmosphere, unperturbed by the presence of emissions from biomass burning, is simulated with inputs of surface sources and deposition of various species measured during ABLE 2A. The presence of haze layers over a region is simulated by the imposition of profiles of species characteristic of haze within the model for 12 hours. The inclusion of hydrocarbons within the modeled haze is found to approximately double the calculated in situ ozone production rate. The difference between the calculated total column ozone production rates in the haze simulation and the background simulation is the model‐predicted enhancement of the in situ ozone production due to regionally transported haze layers (up to 1000 km transport distance). The predicted enhancement of ozone is between 0.3 and 2.9 × 1011molecules O3 cm−2 s−1, near the range of observed rates of ozone increase over the Amazon Basin during the dry season. This suggests that the regional transport of haze during the southern tropical burning season is an important factor in explaining the increase of ozone observed annually during this period.

Ozone climatology at Natal, Brazil, from in situ ozonesonde data

Results are presented from analysis of a large ozone profile data set obtained from balloon ozonesonde soundings made at Natal, Brazil (6°S, 35°W) during the last 10 years (1978–1988). The measurements have been made through an Instituto Nacional de Pesquisas Espaciais (INPE)/NASA long‐term collaboration program. The balloons were released by the Brazilian Air Force at the Natal rocket range. The data set is sufficiently large to provide useful climatology on the average ozone concentration behavior and its seasonal variation. The day‐to‐day ozone concentration variability in the troposphere is rather large, giving standard deviations of about 30–40% for seasonal averages. Maximum ozone concentrations occur during local spring, September–October, and minimum concentrations during late autumn, April‐May. The seasonal variation in the troposphere is much larger than in the stratosphere. If there were no seasonal variation at all in the stratosphere, the seasonal variation observed in the troposphere alone would be strong enough to drive a total ozone column variation of about 5%, which is about one half the size of the variation observed in the Natal Dobson spectrophotometer data. The ozone concentration at Natal increases with height between the surface and about 500 mbar, almost linearly, from about 15 parts per billion by volume (ppbv) to about 38 ppbv, in autumn. For the spring average the ozone concentration increases from about 25 ppbv at the surface to about 66 ppbv at 500 mbar. The sonde data suggest that limitations in aneroid pressure sensors used until 1986 caused the Natal sondes to indicate too much ozone above 6 mbar. Because of the relative sparsity and uneven distribution in time of the ozone soundings, the data are not adequate to study ozone trends. The Dobson data time series shows no definitive ozone trend but displays a pronounced quasi‐biennial oscillation in ozone.

Quantum efficiency for degenerate ρ-type photoluminescence and electroluminescence in GaAs crystals : Huynh Van Cong, Department of Physics, City College of CUNY, New York, NY 10031, U.S.A.

With the beginning of space research in Brazil in the early 60's a national commission for space activities was created. This commission took important steps, in parallel, to create a program of education and training activities that was forseen as of critical importance for the maintainance of a desirable to ambitious degree of space activity in the country. Early efforts were, as a first step, in favour of training of Brazilian students in foreign centers of excellence (mostly in the US and Europe), as a means for achieving the potential human resource necessary for eventual development of a national program. Today a large percentage of the needs in the area is met by programs developed inside the country at different institutions, the most notable being the “Instituto Nacional de Pesquisas Espaciais” -INPE (National Institute for Space Research) at São José dos Campos, where post graduate courses and training programs are well established. Under-graduate courses in selected areas are provided at some Universities, notably at the University of São Paulo. A brief description of the existing programs and an evaluation of the results being achieved are presented in this paper.