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J/A+A/603/A87       Local production rates of 67P/CG from MIRO (Marshall+, 2017)

Spatially resolved evolution of the local H2O production rates of comet 67P/Churyumov-Gerasimenko from the MIRO instrument on Rosetta. Marshall D.W., Hartogh P., Rezac L., von Allmen P., Biver N., Bockelee-Morvan D., Crovisier J., Encrenaz P., Gulkis S., Hofstadter M., Ip W.-H., Jarchow C., Lee S., Lellouch E. <Astron. Astrophys. 603, A87 (2017)> =2017A&A...603A..87M (SIMBAD/NED BibCode)
ADC_Keywords: Comets ; Spectroscopy Keywords: comets: individual: 67P/Churyumov-Gerasimenko - submillimetre: general - techniques: spectroscopic Abstract: Using spectroscopic and continuum data measured by the MIRO instrument on board Rosetta of comet 67P/Churyumov-Gerasimenko, it is possible to derive and track the change in the water production rate, to learn how the outgassing evolves with heliocentric distance. The MIRO data are well suited to investigate the evolution of 67P, in unprecedented spatial and temporal detail. To obtain estimates of the local effective Haser production rates we developed an efficient and reliable retrieval approach with precalculated lookup tables. We employed line area ratios (H216O/H218O) from pure nadir observations as the key variable, along with the Doppler shift velocity, and continuum temperature. This method was applied to the MIRO data from August 2014 until April 2016. Perihelion occurred on August 13, 2015 when the comet was 1.24AU from the Sun. During the perihelion approach, the water production rates increased by an order of magnitude, and from the observations, the derived maximum for a single observation on August 29, 2015 is (1.42±0.51)x1028. Modelling the data indicates that there is an offset in the peak outgassing, occurring 34±10 days after perihelion. During the pre-perihelion phase, the production rate changes with heliocentric distance as rh-3.8±0.2; during post- perihelion, the dependence is rh-4.3±0.2. The comet is calculated to have lost 0.12±0.06% of its mass during the perihelion passage, considering only water ice sublimation. Additionally, this method provides well- sampled data to determine the spatial distribution of outgassing versus heliocentric distance. The time evolution is definitely not uniform across the surface. Pre- and post-perihelion, the surface temperature on the southern hemisphere changes rapidly, as does the sublimation rate with an exponent of ~-6. There is a strong latitudinal dependence on the rh exponent with significant variation between northern and southern hemispheres, and so the average over the comet surface may only be of limited importance. We present more detailed regional variation in the outgassing, thereby demonstrating that the highest derived production rates originate from the Wosret, Neith, and Bes regions during perihelion. Description: The local H2O production rates of the comet 67P/Churyumov-Gerasimenko have been calculated from the lookup table method described in the paper. This uses the spectra measured by MIRO (Microwave Instrument for the Rosetta Orbiter) of the two water lines, H2O16 and H2O18, to find an estimate for the local production rate from the ratio between the two isotopologues. The measured spectra are compared to results from a radiative transfer forward model. Results are given from August 2014 to April 2016. For each date, the following data are provided: the heliocentric distance of the comet, the observed region as defined by El-Maary et al. (2016A&A...593A.110E), the production rate (molec/s), and the error on the measurement (molec/s). object.dat : -------------------------------------------------------------------------------- Code Name Elem q e i H1 d AU deg mag -------------------------------------------------------------------------------- 67P P/Churyumov-Gerasimenko 2454890.5 1.2465141 0.6401757 7.040861 11.63 File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file miroq17.dat 79 3041 Production rate Q data from MIRO
See also: J/A+A/520/A92 : Comet 67P global plasma parameter simulation (Gortsas+ 2010) J/A+A/527/A113 : 67P/Churyumov-Gerasimenko R-band light curve (Tubiana+ 2011) J/A+A/548/A12 : 67P/Churyumov-Gerasimenko R-band light curve (Lowry+, 2012) J/MNRAS/462/S138 : Robotic view of 67P perihelion (Snodgrass+, 2016) J/A+A/600/A3 : Comet ion acoustic waves code (Gunell+, 2017) Byte-by-byte Description of file: miroq17.dat
Bytes Format Units Label Explanations
1- 19 A19 "datime" Date Date and time of observation (YYYY-MM-DDThh:mm:ss) 21- 33 F13.11 AU Rh Heliocentric distance of comet 35- 42 A8 --- Region Region defined by El-Maary et al. (2016A&A...593A.110E) 44- 60 E17.12 mol/s Q Local production rate (in molecule/s) 62- 79 E18.13 mol/s e_Q Error on local production rate (in molecule/s)
Acknowledgements: David Marshall, marshall(at)
(End) Patricia Vannier [CDS] 24-Apr-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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