Tony Travouillon

Exceptional astronomical seeing conditions above Dome C in Antarctica.

One of the most important considerations when planning the next generation of ground-based optical astronomical telescopes is to choose a site that has excellent ‘seeing’—the jitter in the apparent position of a star that is caused by light bending as it passes through regions of differing refractive index in the Earths atmosphere. The best mid-latitude sites have a median seeing ranging from 0.5 to 1.0u2009arcsec (refs 1–5). Sites on the Antarctic plateau have unique atmospheric properties that make them worth investigating as potential observatory locations. Previous testing at the US Amundsen-Scott South Pole Station has, however, demonstrated poor seeing, averaging 1.8u2009arcsec (refs 6, 7). Here we report observations of the wintertime seeing from Dome C (ref. 8), a high point on the Antarctic plateau at a latitude of 75° S. The results are remarkable: the median seeing is 0.27u2009arcsec, and below 0.15u2009arcsec 25 per cent of the time. A telescope placed at Dome C would compete with one that is 2 to 3 times larger at the best mid-latitude observatories, and an interferometer based at this site could work on projects that would otherwise require a space mission.

An analysis of temperatures and wind speeds above Dome C, Antarctica

Department of Geography, University of Idaho, Moscow, Idaho, USA-Abstract. A good astronomical site must fulflll several criteria including low atmospheric turbulence and lowwind speeds. It is therefore important to have a detailed knowledge of the temperature and wind conditions ofa location considered for future astronomical research. Antarctica has unique atmospheric conditions that havealready been exploited at the South Pole station. Dome C, a site located on a local maximum of the Antarcticplateau, is likely to have even better conditions. In this paper we present the analysis of two decades of windspeed measurements taken at Dome C by an automated weather station (AWS). We also present temperature andwind speed proflles taken over four Antarctic summers using balloon-borne weather sondes. We will show that aswell as having one of the lowest average wind speed ever recorded at an existing or potential observatory, DomeC also has an extremely stable upper atmosphere and a very low inversion layer.Key words. Site Testing { Atmospheric afiects { Balloons

Atmospheric turbulence at the South Pole and its implications for astronomy

To investigate the low-atmosphere turbulence at the South Pole, we have measured, using a SODAR, the temperature fluctuation constant (C 2 ) during winter, as a function of altitude up to 890 m. We found that the turbulence was on average concentrated inside a boundary layer sitting below 270 m. While at the peak of winter the turbulence was stable and clearly bounded, during other seasons there was a more complex turbulence profile which extended to higher altitudes. We found that this behaviour could be explained by the horizontal wind speed conditions whose altitude profile closely matched the turbulence profile. We also observed the presence of a vertical wind velocity change of direction at an altitude range corresponding to the turbulent region. The turbulence gives rise to an average seeing of 1:73 00 , which compares poorly with the best astronomy sites. The location of the turbulence, however, means that the seeing quickly decreases above the boundary layer (dropping to 0:37 00 above 300 m). We also have recorded the largest isoplanatic angle (AO= 3:3 00 ) and the longest coherence time (AO= 2: 9m s)

Site testing in summer at Dome C, Antarctica

We present summer site testing results based on DIMM data obtained at Domexa0C, Antarctica. These data were collected on the bright star Canopus during two 3-months summer campaigns in 2003-2004 and 2004-2005. We performed continuous monitoring of the seeing and the isoplanatic angle in the visible. We found a median seeing of 0.54´´u2000and a median isoplanatic angle of 6.8´´. The seeing appears to have a deep minimum around 0.4´´u2000almost every day in late afternoon.

A search for propylene oxide and glycine in Sagittarius B2 (LMH) and Orion

We have used the Mopra Telescope to search for glycine and the simple chiral molecule propylene oxide in the Sgr B2 (LMH) and Orion KL, in the 3-mm band. We have not detected either species, but have been able to put sensitive upper limits on the abundances of both molecules. The 3 sigma upper limits derived for glycine conformer I are 3.7 x 10(14) cm(-2) in both Orion-KL and Sgr B2 ( LMH), comparable to the reported detections of conformer I by Kuan et al. However, as our values are 3s upper limits rather than detections we conclude that this weighs against confirming the detection of Kuan et al. We find upper limits for the glycine II column density of 7.7 x 10(12) cm(-2) in both Orion-KL and Sgr B2 ( LMH), in agreement with the results of Combes et al. The results presented here show that glycine conformer II is not present in the extended gas at the levels detected by Kuan et al. for conformer I. Our ATCA results have ruled out the detection of glycine ( both conformers I and II) in the compact hot core of the LMH at the levels reported, so we conclude that it is unlikely that Kuan et al. have detected glycine in either Sgr B2 or Orion-KL. We find upper limits for propylene oxide abundance of 3.0 x 10(14) cm(-2) in Orion-KL and 6.7 x 10(14) cm(-2) in Sgr B2 (LMH). We have detected fourteen features in Sgr B2 and four features in Orion-KL which have not previously been reported in the interstellar medium, but have not been able to plausibly assign these transitions to any carrier.

Thirty Meter Telescope Site Testing V: Seeing and Isoplanatic Angle

In this article we present an analysis of the statistical and temporal properties of seeing and isoplanatic angle measurements obtained with combined Differential Image Motion Monitor (DIMM) and Multi-Aperture Scintillation Sensor (MASS) units at the Thirty Meter Telescope (TMT) candidate sites. For each of the five candidate sites we obtained multiyear, high-cadence, high-quality seeing measurements. These data allow for a broad and detailed analysis, giving us a good understanding of the characteristics of each of the sites. The overall seeing statistics for the five candidate sites are presented, broken into total seeing (measured by the DIMM), free-atmosphere seeing and isoplanatic angle (measured by the MASS), and ground-layer seeing (difference between the total and free-atmosphere seeing). We examine the statistical distributions of seeing measurements and investigate annual and nightly behavior. The properties of the seeing measurements are discussed in terms of the geography and meteorological conditions at each site. The temporal variability of the seeing measurements over timescales of minutes to hours is derived for each site. We find that each of the TMT candidate sites has its own strengths and weaknesses when compared against the other candidate sites. The results presented in this article form part of the full set of results that are used for the TMT site-selection process. This is the fifth article in a series discussing the TMT site-testing project.

Automated Shack-Hartmann seeing measurements at the South Pole

The statistics and dynamics of the atmospheric seeing at the South Pole have been studied over a period of 101 days in winter. These measurements have been made with the first fully autonomous dierential image motion monitor, the A-DIMM. The analysis shows an average seeing of 1:9 00 with a standard deviation of 0:6 00 . The extensive set of data has allowed the study of the seeing time variations, showing that the seeing varies by a factor of two within a characteristic time of 2 hours.

The Antarctic planet interferometer

The Antarctic Planet Interferometer is a concept for an instrument designed to detect and characterize extrasolar planets by exploiting the unique potential of the best accessible site on earth for thermal infrared interferometry. High-precision interferometric techniques under development for extrasolar planet detection and characterization (differential phase, nulling and astrometry) all benefit substantially from the slow, low-altitude turbulence, low water vapor content, and low temperature found on the Antarctic plateau. At the best of these locations, such as the Concordia base being developed at Dome C, an interferometer with two-meter diameter class apertures has the potential to deliver unique science for a variety of topics, including extrasolar planets, active galactic nuclei, young stellar objects, and protoplanetary disks.

Boundary layer seeing measurements in the Canadian High Arctic

As part of a program to measure and evaluate atmospheric turbulence on mountains at the most northerly tip of North America, we have deployed two SODARs and a lunar scintillometer at the Polar Environment Atmospheric Research Lab (PEARL) located on a 600m-high ridge near Eureka on Ellesmere Island, at 80° latitude. This paper discusses the program and presents a summary of ground-layer turbulence and seeing measurements from the 2009-10 observing season.

Extrasolar planet science with the Antarctic planet interferometer

The primary limitation to ground based astronomy is the Earths atmosphere. The atmosphere above the Antarctic plateau is different in many regards compared to the atmosphere at temperate sites. The extreme altitude, cold and low humidity offer a uniquely transparent atmosphere at many wavelengths. Studies at the South Pole have shown additionally that the turbulence properties of the night time polar atmosphere are fundamentally different to mid latitudes. Despite relatively strong ground layer turbulence, the lack of high altitude turbulence combined with low wind speeds presents favorable conditions for interferometry. The unique properties of the polar atmosphere can be exploited for Extrasolar Planet studies with differential astrometry, differential phase and nulling intereferometers. This paper combines the available data on the properties of the atmosphere at the South Pole and other Antarctic plateau sites for Extrasolar Planet science with interferometry.