55 research outputs found
Earth radiation budget measurement from a spinning satellite: Conceptual design of detectors
The conceptual design, sensor characteristics, sensor performance and accuracy, and spacecraft and orbital requirements for a spinning wide-field-of-view earth energy budget detector were investigated. The scientific requirements for measurement of the earth's radiative energy budget are presented. Other topics discussed include the observing system concept, solar constant radiometer design, plane flux wide FOV sensor design, fast active cavity theory, fast active cavity design and error analysis, thermopile detectors as an alternative, pre-flight and in-flight calibration plane, system error summary, and interface requirements
Saturn's Seasonal Atmosphere at Northern Summer Solstice
The incredible longevity of Cassini's orbital mission at Saturn has provided
the most comprehensive exploration of a seasonal giant planet to date. This
review explores Saturn's changing global temperatures, composition, and aerosol
properties between northern spring and summer solstice (2015-2017), extending
our previous review of Cassini's remote sensing investigations (2004-14,
Fletcher et al., 2018) to the grand finale. The result is an unprecedented
record of Saturn's climate that spans almost half a Saturnian year, which can
be used to test the seasonal predictions of radiative climate models, neutral
and ion photochemistry models, and atmospheric circulation models. Hemispheric
asymmetries in tropospheric and stratospheric temperatures were observed to
reverse from northern winter to northern summer; spatial distributions of
hydrocarbons and para-hydrogen shifted in response to atmospheric dynamics
(e.g., seasonally-reversing Hadley cells, polar stratospheric vortex formation,
equatorial stratospheric oscillations, and inter-hemispheric transport); and
upper tropospheric and stratospheric aerosols exhibited changes in optical
thickness that modulated Saturn's visible colours (from blue hues to a golden
appearance in the north near solstice), reflectivity, and near-infrared
emission. Numerical simulations of radiative balance and photochemistry do a
good job in reproducing the observed seasonal change and phase lags, but
discrepancies between models and observations still persist, indicating a
crucial role for atmospheric dynamics and the need to couple chemical and
radiative schemes to the next generation of circulation models. With Cassini's
demise, an extended study of Saturn's seasons, from northern summer to autumn,
will require the capabilities of ground- and space-based observatories, as we
eagerly await the next orbital explorer at Saturn.Comment: 24 pages, 18 figures, submitted for publication by Cambridge
University Press as part of a multi-volume work edited by Kevin Baines,
Michael Flasar, Norbert Krupp, and Thomas Stallard, entitled "Cassini at
Saturn: The Grand Finale." The copy of the Chapter, as displayed on this
website, is a draft, pre-publication copy onl
A study to define meteorological uses and performance requirements for the Synchronous Earth Observatory Satellite
The potential meteorological uses of the Synchronous Earth Observatory Satellite (SEOS) were studied for detecting and predicting hazards to life, property, or the quality of the environment. Mesoscale meteorological phenonmena, and the observations requirements for SEOS are discussed along with the sensor parameters
Pioneer Venus 12.5 km Anomaly Workshop Report, volume 1
A workshop was convened at Ames Research Center on September 28 and 29, 1993, to address the unexplained electrical anomalies experienced in December 1978 by the four Pioneer Venus probes below a Venus altitude of 12.5 km. These anomalies caused the loss of valuable data in the deep atmosphere, and, if their cause were to remain unexplained, could reoccur on future Venus missions. The workshop participants reviewed the evidence and studied all identified mechanisms that could consistently account for all observed anomalies. Both hardware problems and atmospheric interactions were considered. Based on a workshop recommendation, subsequent testing identified the cause as being an insulation failure of the external harness. All anomalous events are now explained
Spectral determination of the colour and vertical structure of dark spots in Neptune’s atmosphere
Previous observations of dark vortices in Neptune’s atmosphere, such as Voyager 2’s Great Dark Spot (1989), have been made in only a few broad-wavelength channels, hampering efforts to determine these vortices’ pressure levels and darkening processes. We analyse spectroscopic observations of a dark spot on Neptune identified by the Hubble Space Telescope as NDS-2018; the spectral observations were made in 2019 by the Multi Unit Spectroscopic Explorer (MUSE) of the Very Large Telescope (Chile). The MUSE medium-resolution 475–933 nm reflection spectra allow us to show that dark spots are caused by darkening at short wavelengths (700 nm). This bright feature is much deeper than previously studied dark-spot companion clouds and may be connected with the circulation that generates and sustains such spots
Spectral determination of the colour and vertical structure of dark spots in Neptune's atmosphere
Previous observations of dark vortices in Neptune's atmosphere, such as
Voyager-2's Great Dark Spot, have been made in only a few, broad-wavelength
channels, which has hampered efforts to pinpoint their pressure level and what
makes them dark. Here, we present Very Large Telescope (Chile) MUSE
spectrometer observations of Hubble Space Telescope's NDS-2018 dark spot, made
in 2019. These medium-resolution 475 - 933 nm reflection spectra allow us to
show that dark spots are caused by a darkening at short wavelengths (< 700 nm)
of a deep ~5-bar aerosol layer, which we suggest is the HS condensation
layer. A deep bright spot, named DBS-2019, is also visible on the edge of
NDS-2018, whose spectral signature is consistent with a brightening of the same
5-bar layer at longer wavelengths (> 700 nm). This bright feature is much
deeper than previously studied dark spot companion clouds and may be connected
with the circulation that generates and sustains such spots.Comment: 1 table. 3 figures. Nature Astronomy (2023
Gas Giants
The gas giants (Jupiter and Saturn) and icy giants (Uranus and Neptune) are fluid planets with atmospheres primarily made of hydrogen and helium. The part of their atmospheres accessible to remote sensing occupies only a small fraction of their radii (0.05%). Clouds and hazes form around the 1 bar altitude pressure level and extend vertically, according to the thermochemical models, in a layer with a thickness of 200_500 km where temperature increases with depth (usually known as the "weather layer"). Clouds made of NH3, NH4SH, H2O (in Jupiter and Saturn), with the addition of CH4 (in Uranus and Neptune), cover the planet in stratified layers that are mixed with unknown hromophore agents. Dynamical phenomena in the weather layer shape different cloud patterns that define the visible appearance of these planets. In the thermal part of the spectrum clouds act as opacity sources providing brightness contrasts. The ensemble of cloud morphologies in terms of shapes, sizes and albedos allows their use as tracers of the atmospheric motions in the weather layer (Fig. 4.1). This is the main tool employed so far to study the winds on these fourplanets
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