Raw Data Releases
Raw Data Releases consist of IBEX-Hi and IBEX-Lo direct event and histogram files and supporting files. These files can be used to generate maps similar to maps produced by the IBEX SOC.
Filename Description
Data files are named using keywords that indicate the type of data they contain:
- hide-n - IBEX-Hi direct events for energy step n
- lode-n - IBEX-Lo direct events for energy step n
- hihb-n - IBEX-Hi histogram events for energy step n
- lohb-n - IBEX-Lo histogram events for energy step n
- star-spin-nep - star sensor data
- .attdba - quaternions
- ibex_state_GSE - IBEX state vectors
File Column Descriptions
Description of the columns in the direct event and histogram files:
MET – The timestamp (MET) derived from the s/c clock which is set to the number of seconds in the GPS epoch near the perigee of each orbit. (The GPS epoch starts at Sat->Sun midnight on Jan 6, 1980, when the Global Positioning System was activated.) The IBEX clock is not well regulated, so the correlation with the times on other s/c or the ground is not likely to be better than a few minutes. For a DE, this time is the arrival time of the event. For a HB, it is the start of the interval over which the events were collected. Note that during this time, the electrostatic analyzer (ESA) sweeps through several energy steps (6 for Hi, 8 for Lo).
R.A. and Decl. – The celestial source (assuming a straight line-trajectory from the HS) of a single direct event (DE) or histogram bin (HB) is given as R.A. and Decl. in the J2000 celestial coordinate system. Obviously, the trajectory is not a straight-line, so these are really statements about arrival direction, bearing in mind that the collimator FWHM is about 14 degrees and the event timing limits accuracy to 0.1 deg or so. For the case of histogram bins, this is the center of a 6-deg sky bin.
ch – This two-digit hexadecimal value encodes two data elements. The high-order (left-most) digit is the species:
| Hi | Lo |
|---|---|
| 1 | 2 - Hydrogen 4 - Oxygen |
The low-order (right-most) digit is the ESA (1 - 6 for Hi; 1 - 8 for Lo).
ty – This two-digit hexadecimal value also encodes two data elements. The high-order (left-most) digit is the sensor type:
| File | Value |
|---|---|
| Hi DE | 0 |
| Hi HB | 1 |
| Lo DE | 4 |
| Lo HB | 8 - 6 degree histograms C - 60 degree monitors |
The low-order (right-most) digit is the coincidence type:
| Hi Direct Event | ||||||
|---|---|---|---|---|---|---|
| Hex | type | octal | binary | abcABC | LongH | QualH |
| A | 10 | 047 | 100111 | a‐‐ABC | L-ABC | Q-ABC |
| 5 | 5 | 027 | 010111 | -b-ABC | L-ABC | Q-ABC |
| E | 14 | 067 | 110111 | ab-ABC | L-ABC | Q-ABC |
| C | 12 | 057 | 101111 | a-cABC | L-ABC | - |
| F | 15 | 077 | 111111 | abcABC | L-ABC | - |
| 7 | 7 | 037 | 011111 | -bcABC | L-ABC | - |
| 2 | 2 | 017 | 001111 | ‐‐cABC | L-ABC | - |
| 9 | 9 | 046 | 100110 | a‐‐AB- | L-AB | Q-AB |
| D | 13 | 066 | 110110 | ab-AB- | L-AB | Q-AB |
| 4 | 4 | 026 | 010110 | -b-AB- | L-AB | Q-AB |
| 3 | 3 | 023 | 010011 | -b‐‐BC | L-BC | Q-BC |
| 6 | 6 | 033 | 011011 | -bc-BC | L-BC | - |
| 0 | 0 | 013 | 001011 | ‐‐c-BC | L-BC | - |
| 8 | 8 | 045 | 100101 | a‐‐A-C | L-AC | Q-AC |
| B | 11 | 055 | 101101 | a-cA-C | L-AC | - |
| 1 | 1 | 015 | 001101 | ‐‐cA-C | L-AC | - |
Events are named according to the bits present at the end of the short and long windows. The binary and abcABC notations are both in use; the type numbers are the order of the events expressed in octal (base 8), but appear in Hex in the event listings.
| Event | Description |
|---|---|
| abc | the ABC pulses latched after the short window (3 bits) |
| ABC | the ABC pulses latched after the long window (3 bits) |
| L-??? | Long count coincidence histogram group (named after the set of CEM bits present at the end of the long window, and independent of the bits present at the end of the short window) |
| Q-??? | Qualified count coincidence histogram group (named after the set of CEM bits present at the end of the long window) |
| Hi histograms | |
|---|---|
| 0 | Q-ABC |
| 1 | Q-AB |
| 2 | Q-BC |
| 3 | Q-AC |
| 4 | L-ABC |
| 5 | L-AB |
| 6 | L-BC |
| 7 | L-AC |
There are 16 IBEX-Lo direct event coincidence types. They are classified based on whether the corresponding time-of-flight (TOF) measurement between the start/stop points in the detector are valid. There are 4 such points: a is a start, b0 and b3 are stops, and c is an intermediate surface where both stops and starts may be generated.
There are two surfaces inside the TOF chamber through which ions pass and are eventually detected at the microchannel plate (MCP). When a negative ion hits the first foil it emits an electron which is almost immediately received at the MCP; that is the first start, ‘a’. Next ions and neutrals reach the second foil, emit another electron which is immediately received as the second start, ‘c’. Finally, ions and neutrals are received at the MCP as a stop ‘b?’ (? = 0,1,2,3). If there is one start and one stop for an event then it is a ‘double’ event. If there are two valid starts and a stop then it is called a ‘triple’ event.
TOF0=b0-a
TOF1=b3-c
TOF2=c-a
TOF3=b3-b0
| Value | TOF Flags | Note flag | Meaning |
|---|---|---|---|
| 0123 | |||
| 0 | 0000 | $ | Triple (=> a,b0,b3,c; golden/all valid) |
| 1 | 0001 | - | Triple (=> a,b0,b3,c; TOF3 invalid) |
| 2 | 0010 | - | Triple (=> a,b0,b3,c; TOF2 invalid) |
| 3 | 0011 | - | Triple (=> a,b0,b3,c; TOF2 & TOF3 invalid) |
| 4 | 0100 | - | Triple (=> a,b0,b3,c; TOF1 invalid) |
| 5 | 0101 | . | Triple (=> a,b0, c; TOF1 & TOF3 invalid) |
| 6 | 0110 | $ | Double (=> a,b0,b3 ; TOF1 & TOF2 invalid) |
| 7 | 0111 | . | Double (=> a,b0 ; only TOF0 valid) |
| 8 | 1000 | - | Triple (=> a,b0,b3,c; TOF0 invalid) |
| 9 | 1001 | . | Triple (=> a, b3,c; TOF0 & TOF3 invalid) |
| A | 1010 | + | Double (=> b0,b3,c; TOF0 & TOF2 invalid) |
| B | 1011 | . | Double (=> b3,c; only TOF1 valid) |
| C | 1100 | - | Triple (=> a,b0,b3,c; TOF0 & TOF1 invalid) |
| D | 1101 | $ | Double (=> a, c; only TOF2 valid) |
| E | 1110 | x | Single (=> b0,b3 ; only TOF3 valid) |
| F | 1111 | x | Absent (=> ; nothing valid) |
| TOF Flags | |
|---|---|
| TOF Flag Position | Meaning |
| 0 | TOF0 not absent => a & b0 present & TOF valid |
| 1 | TOF1 not absent => b3 & c present & TOF valid |
| 2 | TOF2 not absent => a & c present & TOF valid |
| 3 | TOF3 not absent => b0 & b3 present & TOF valid |
| Note flags | |
|---|---|
| Note flag | Meaning |
| - | not likely, but still physical |
| . | one of b0 or b3 missing, (not likely but still physical) |
| x | useless events |
| $ | the most likely possibilities |
| + | good events with some outliers |
| Lo Histogram events | |
|---|---|
| 1 | Hydrogen |
| 2 | Oxygen |
count – 1 for a DE; for HB, it is the approximate number of counts. (The telemetry system uses a compression scheme.)
selnbits – not used
phase - The phase column expresses the arrival time of the event (or center of a sky bin) expressed as the fraction of a spin between spin pulses. The spin pulse is triggered 3 deg before IBEX-Hi is pointed at the North Ecliptic Pole (NEP) and IBEX-Lo is pointed at the South Ecliptic Pole (SEP). Thus, the NEP is phase = 0.0083 in IBEX-Hi and 0.5083 for IBEX-Lo. (The R.A. and Decl values are derived from this together with the detailed s/c attitude information.)
loc-X/Y/Z-RE - The "loc-*-RE" columns record the position of IBEX relative to the Earth in Earth Radii in the same J2000 inertial reference frame as R.A. and Decl.
star-spin-nep file
This file contains star sensor voltage data. There is a column for each spin and the rows are NEP angles in 0.5 degree increments from -3 degrees to 357 degrees.
.attdba/.attd2a file
The first column is MET time; the following four columns are a quaternion.
If the file extension is .attd2a the orbit required despinning.
ibex_state_GSE file
The first column is MET time, the next three columns are the x/y/z value of the IBEX position vector (km) and the next three columns are the corresponding velocity vector (km/s). The state vectors are IBEX relative to Earth.