Data Release 6

Data Release 6 Index:
Solar Radiation and ISM Flow    Inertial Pointing    Primary H Data Rates    Interstellar He Data Files    Collimator Function    IBEX State Vectors

Solar Radiation Pressure And Local Interstellar Medium Flow Parameters From Interstellar Boundary Explorer Low Energy Hydrogen Measurements

Neutral hydrogen atoms that travel into the heliosphere from the local interstellar medium (LISM) experience strong effects due to charge exchange and radiation pressure from resonant absorption and re-emission of Lyα. The radiation pressure roughly compensates for the solar gravity. As a result, interstellar hydrogen atoms move along trajectories that are quite different than those of heavier interstellar species such as helium and oxygen, which experience relatively weak radiation pressure. Charge exchange leads to the loss of primary neutrals from the LISM and the addition of new secondary neutrals from the heliosheath. IBEX observations show clear effects of radiation pressure in a large longitudinal shift in the peak of interstellar hydrogen compared with that of interstellar helium.  Here, we compare results from the Lee et al. interstellar neutral model with IBEX-Lo hydrogen observations to describe the distribution of hydrogen near 1 AU and provide new estimates of the solar radiation pressure. We find over the period analyzed from 2009 to 2011 that radiation pressure divided by the gravitational force (μ)has increased slightly from μ = 0.94 ± 0.04 in 2009 to μ = 1.01 ± 0.05 in 2011. We have also derived the speed, temperature, source longitude, and latitude of the neutral H atoms and find that these parameters are roughly consistent with those of interstellar He, particularly when considering the filtration effects that act on H in the outer heliosheath. Thus, our analysis shows that over the period from 2009 to 2011, we observe signatures of neutral H consistent with the primary distribution of atoms from the LISM and a radiation pressure that increases in the early rise of solar activity.

Intertial Pointing Memo 5.16.2014

Intertial Pointing Memo-5.16.2014_EM2.PDF

Inertial Pointing File Text File

Primary Hydrogen Data Rate Files

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Data rate files are listed by orbit number:


where XX corresponds to the orbit number. The format is listed below. 

The data rate files contain five data columns correspond to:
isector, rate (ESA1), uncertainty(ESA1), rate(ESA2), uncertainty (ESA2).

All rates in counts/sec.

The methods used to estimate these background-corrected count rates are discussed by Schwadron et al. (2013). Because of background correction some of the listed rates are negative, but these are typically negative values near 0 within statistical uncertainties. 

isector: 0 - 30
isector corresponds to the spin-sector of the IBEX-Hi sensor

The spinning spacecraft moves the sensors from 0 to 360 in a great-circle where the spin-axis is directed with RA and DEC coordinates given in the inertial pointing file. Sector 0 corresponds to the spin sector whose center in spin angle points exactly to the North Ecliptic Pole (NEP).

hi-spinphase (deg) = isector*6.0 

lo-spinphase (deg) = hi-spinphase +/- 180.0

He Data (Sputtered H) Count Files

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Data rate files are listed by orbit number:
where XX corresponds to the orbit number and Y to the sequence number of separately listed time periods in the respective orbit. The format in the file is listed 
below. The data are given accumulated over 512 spins each (≈ 2 hours) in time blocks separated by dashed lines.
Provided are the data for the “Good Times for Angular Distributions” given in Table 1 by 
MÖBIUS ET AL. (2012, APJ SUPPL, 198, 11, DOI:10.1088/0067-0049/198/2/11).
The description of the data selection is found in the file MÖBIUS_etal_2012-APJ-suppl_data-description.pdf

These data were released as aggregate data for the entire time periods listed along with the publication of the 2012 ApJ Suppl publications. 

In the current compilation, the time periods have been sub-divided into 512-spin time periods and thus synchronized with the internal accumulation periods of the onboard Histograms reported here and with the prescribed 512-spin accumulation. Therefore, some of the periods have slightly different start times and truncated to match the last complete 512-spin period at the end. Orbit 13 was omitted from the current compilation because several data gaps due to still ongoing commanding during that orbit cut into the prescribed 512 spin cadence. Also, in Data Release 3, the start and end times were slightly different from Table 1 to match the cadence chosen for the data.

As used in the 2012 ApJ Suppl publications, Golden Triple Hydrogen counts detected in IBEX-Lo energy step 2 in 6o resolution are reported, which reflect H sputtered off the IBEX-Lo conversion surface by incoming interstellar He, as described in Möbius et al. (2012).

The data rate files are organized as follows: 
The first line in the header contains column labels for 6 data columns, as listed below 
The next header line includes the start time (in GPS), end time (in GPS), and accumulated time (in seconds). This line is repeated for each 512-spin time period.
Column 1 : The center of each 6 degree angular bin in NEP as calculated using the phase in the HB file. 
0 – 354 Degrees corresponds to the spin-angle counted from the North Ecliptic Pole (NEP). The spinning spacecraft moves both sensors
from 0 to 360 in a great-circle where the spin-axis is
directed with RA and DEC coordinates given in the 
inertial pointing file. Spin angle 0 corresponds to the spin sector whose center in spin angle points exactly to the North Ecliptic Pole (NEP).
Column 2 : Start time of the 512 spin bin in GPS
Column 3 : Start time of the 512 spin bin in YYYY/MM:DD:HH:MM:SS format
Column 4 : Counts in the Hydrogen histogram bins (HB-Counts)
Column 5 : Same as column 1 except this was determined from the DE file, here as a check to make sure there were no missing bins in the HB file
Column 6 : Counts listed as GOLDEN HYDROGEN in the direct events (DE_Counts)

Note: The HB_Counts are used in the analysis to normalized DE_Counts for digital buffer and telemetry limitations during high count rate time periods, as they occur during the interstellar flow observations. Usually, HB_Counts ≥ DE_Counts. However, during times when the count rates do not exceed the telemetry capability or not by much, occasionally DE_Counts > HB_Counts due to the finite digital angular binning by time increments of 4.1 ms, equivalent to ≈ 0.075o in spin angle, which can lead to different binning in DE and HB at the boundaries of the 6o angular bins. Still, the HB_Count normalization should be used. The related angular uncertainty of the accumulated counts is ≤0.075o and thus smaller than the overall pointing accuracy as reported by Hlond et al. (2012, ApJ Suppl, 198, 9, doi:10.1088/0067-0049/198/2/9)

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Collimator Function

Coll-FoV_PointSpread.csv (EXCEL file)


IBEX State Vectors