ACE/MAG Release Notes: The following are cummulative release notes for the ACE Magnetic Field Instrument (MAG) Level-2 datasets. As new datasets are released or old datasets are processed, this file will be updated. ------------------------------------------------------------------- August 10, 1998: Release of DOY 1 -- 120 of 1998, Version 1 of MAG Level-2 data in RTN coordinates. Each data file contains documentation of maneuver times, field components in RTN, |B|, latitude and longitude, and RMS values of underlying high-resolution measurements. Data are 16-second averages of the vector measurements. The datafiles are processed based on daily files of Level-1 data. Bad or missing data is filled with -999.9, except at beginning or end of day when data is not supplied. Time tags are approximate and good to better than 16 seconds. ACE frame counts are exact and mark the beginning of the data averaging interval. Use of single initial zeroes file for all of 120 day interval. Results good to 1/3 nT. Final alignment of sensors not yet performed, but correction expected to be smaller than above. Release of daily graphics files included at same time. Release of revised Level-2 data anticipated shortly. ------------------------------------------------------------------- March 5, 1999 Release of DOY 121 -- 300 of 1998, Version 1 of MAG Level-2 data in RTN coordinates. Formats for data files are the same as before, except that headers are extended to include maneuver times, spacecraft location at beginning and end of the interval, and spacecraft attitude at same times. Release of daily graphics files included at same time. Graphics revised to include above additional header material. Two days (DOY 263 and DOY 278) remain suspect with possibly analysis issues for Range-0 (low |B|) data. Further analysis of these days is ongoing. A revision of 1998 (Version 2) will be filed at a later date. -------------------------------------------------------------------- August 10, 1999 Release of DOY 301 -- 365 of 1998, Version 1 of MAG Level-2 data in RTN coordinates. Formats for data files are unchanged. Release of daily graphics files included at same time. -------------------------------------------------------------------- August 12, 1999 Release of DOY 1 -- 30 of 1999, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily graphics files at same time. Data and plot formats are unchanged. --------------------------------------------------------------------- September 29, 1999 Release of DOY 31 -- 109 of 1999, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily graphics files at same time. --------------------------------------------------------------------- October 18, 1999 Release of DOY 152 -- 265 of 1999, Version 1 of MAG Level-2 data in RTN coordinates. Release of this data interval is out of sequence with previous release in order for ACE to support Cassini flyby of Earth. Release of daily graphics files at same time. --------------------------------------------------------------------- October 21, 1999 Release of DOY 110 -- 151 of 1999, Version 1 of MAG Level-2 data in RTN coordinates. Release of this data interval brings MAG release to DOY 265 of 1999. Release of daily graphics files at same time. --------------------------------------------------------------------- December 10, 1999 Two problems (one real and one potential) have come to the attention of the ACE/MAG team and must be acknowledged for the sake of those using MAG data. 1) Although the ground processing software (Level-2, Browse, and RTSW codes) was designed to use -999.9 as badpoint values so that "0" values should never appear in the dataset, it is now known that Level-2 data does possess some frames with these values. They appear in 1/2 major frame subsets and the source is not yet known. 2) The sunpulse anomaly of June 1999 may result in minor errors in the spin period, which can result in spin tones and errors in despun coordinate systems (RTN, GSE, etc.). If so, the errors will be small. The dates and times for when this anomaly may influence the data are from 13:50 June 5 until 16:00 June 12. --------------------------------------------------------------------- March 1, 2000 Release of DOY 266 of 1999 -- DOY 57 of 2000, Version 1 of MAG Level-2 data in RTN coordinates. Release of this data interval brings MAG release to DOY 057 of 2000. Release of daily graphics files at same time. Source of |B|=0 values not yet determined, but such values should be searched for in any analysis and the points treated as bad values. --------------------------------------------------------------------- June 23, 2000 Release of DOY 58 of 2000 -- DOY 169 of 2000, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily graphics files at same time. --------------------------------------------------------------------- October 13, 2000 Release of DOY 170 of 2000 -- DOY 271 of 2000, Version 1 of MAG Level-2 data in RTN coordinates. Apparently unphysical RMS signatures during maneuver of DOY 230 that do not show up as shifts in mean field. Source not known at present. There continue to be intervals (generally short lasting a few hours to a day) when the apparent zero level of the combined spacecraft + instrument signal abruptly changes by < 0.5 nT (usually). Since the shift sometimes occurs primarily along the spin axis of the spacecraft, we are not confident that we always resolve these events and the user should remain aware that at present such events may remain unresolved. The source(s) of these events is under investigation. Release of daily graphics files at same time. --------------------------------------------------------------------- April 5, 2001 Release of DOY 272 of 2000 -- DOY 353 of 2000, Version 1 of MAG Level-2 data in RTN coordinates. The source(s) of spacecraft field remain unresolved. Zeroes are quite good for all three instrument ranges of interest at L1. No strikingly anomalous signals are seen in this time, but continued analysis in scientific efforts may always reveal previously unknown problems. B=(0,0,0) values in processed data appear to persist, but source has never been identified and they must be treated as bad data. Release of daily graphics files at same time. --------------------------------------------------------------------- April 6, 2001 Release of DOY 354 of 2000 -- DOY 040 of 2001, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- May 18, 2001 Release of DOY 41 of 2001 -- DOY 120 of 2001, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- January 4, 2002 Release of DOY 121 of 2001 -- DOY 166 of 2001, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- January 7, 2002 Release of DOY 167 of 2001 -- DOY 365 of 2001, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. Odd behavior during maneuver on DOY 205 (July 24, 2001). RMS levels change by ~0.5 nT in step fashion several times although instrument range does not change. Probably unresolved spacecraft signal, but data is not guaranteed during maneuvers. ACE Science Center informs us that: Larger than usual number of missing minor frames in telemetry for DOYs 351 (~0.6%) and 352 (~4%). This does not interfere with processing or overall data quality of MAG data. Attitude data for DOYs 356-360, inclusive, inaccurate to ~1 degree due to errors in the star scanner. --------------------------------------------------------------------- July 16, 2002 Release of DOY 248 of 1997 -- DOY 365 of 1997, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. MAG was only instrument on and taking data at this time, so there has been little call for the 1997 data. Days 342-347 and 349 are missing due to halo insertion maneuver. There was no science telemetry at this time. The first 11 days of flight are difficult to analyze due to many reasons. However, at least some fraction of these will be released shortly following further analysis. Several days show anomalous behavior: Days 250-253 show odd 30-minute oscillation similar to that seen during first 11 days of mission. Odd stepping in fluctuation level on days 258, 262, 266, 267, and 353. Zeroes appear to step briefly on days 276-277, 289, 302-304, 316-317, and 332-333. Both of the above effects are at the < 0.5 nT level. Sources of the above behavior have not been identified, but further effort to refine the data will probably reduce or eliminate the effect. --------------------------------------------------------------------- July 17, 2002 Release of DOY 245 of 1997 -- DOY 247 of 1997, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. ACE was launched on DOY 237 of 1997. Data from launch through DOY 244 shows more rapidly changing zeroes of undetermined origin than is seen in the remainder of the mission to date. A future version of the MAG processing software will better handle this situation. Since this data is not now up to the standards of the ACE/MAG instrument team, we are not releasing these 8 days of data to the general public at this time. If data from these 8 days are desired, please contact the ACE/MAG team and arrangements can be made to deliver the data in the best form available and at the same time that the appropriate warnings regarding data quality during this time can be provided. --------------------------------------------------------------------- July 29, 2002 Rerelease of DOY 001 of 1998 -- DOY 300 of 1998, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. This release was motivated by an ASC request to standardize MAG data deposits in a form opiginally established with 1998-301 data. This format contains the complete spacecraft position information that has been standard ever since. The data released now should be identical to that which was released earlier, but in fact there are small differences. Early in 1998 the data time tag used by the MAG team was approximate. It is now correct. Also, small changes in the computed IMF have resulted from changes in the analysis program. Generally, the changes are small. The largest changes are seen on days 121 through 160 when changes up to 0.15 nT are seen. Generally, but not always, the change results from better zeroes and contains a smaller spin tone. A formal release of Version 2 data is still intended that will contain additional changes to the processing, but for now no version number other than 1 is attached to this data. --------------------------------------------------------------------- August 4, 2002 Release of DOY 001 of 2002 -- DOY 146 of 2002, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. Zeroes processing uncovered interesting oscillations in the spacecraft field starting ~ day 30 and continuing to at least day 73. The period of the oscillations is ~8 days. The amplitude is ~0.12 nT at both sensors. Data continue to have occasional B=(0,0,0) and Bmag=0 values arising from unresolved processing source. Values appear in 8-s blocks with multiple contiguous 8-s blocks possible. User is advised to test for this condition as well as the badpoint flag -999.9 and treat both as unphysical. --------------------------------------------------------------------- September 16, 2002 Release of DOY 147 of 2002 -- DOY 203 of 2002, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. June 26, 2002 (DOY 177) from ~9:30 to ~11:00 UT contains telemetry errors. Resulting MAG analysis yields B=(0,0,0) and Bmag=0 arising from unresolved processing source. User is advised to test for this condition as well as the badpoint flag -999.9 and treat both as unphysical. --------------------------------------------------------------------- September 18, 2002 Release of DOY 204 of 2002 -- DOY 208 of 2002, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- January 4, 2003 Release of DOY 209 of 2002 -- DOY 235 of 2002, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- January 6, 2003 Release of DOY 236 of 2002 -- DOY 262 of 2002, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- May 5, 2003 Release of DOY 264 of 2002 -- DOY 343 of 2002, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- September 23, 2003 Release of DOY 344 of 2002 -- DOY 032 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- October 22, 2003 Release of DOY 33 of 2003 -- DOY 059 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- October 23, 2003 Release of DOY 60 of 2003 -- DOY 086 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. 9.5 hour data gap on day 71 (March 12). --------------------------------------------------------------------- October 30, 2003 Release of DOY 87 of 2003 -- DOY 113 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- November 2, 2003 Release of DOY 114 of 2003 -- DOY 140 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- November 21, 2003 Release of DOY 141 of 2003 -- DOY 167 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. Note: Less than 2 hours of data are missing on day 142, from ~15:10 until 17:00 UT. This is due to spacecraft being in ADC mode. This data is available upon request by special processing. --------------------------------------------------------------------- December 1, 2003 Release of DOY 168 of 2003 -- DOY 248 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- December 10, 2003 Release of DOY 249 of 2003 -- DOY 302 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- December 12, 2003 Release of DOY 303 of 2003 -- DOY 329 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- March 24, 2004 Release of DOY 330 of 2003 -- DOY 357 of 2003, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. --------------------------------------------------------------------- June 24, 2004 Release of DOY 358 of 2003 -- DOY 72 of 2004, Version 1 of MAG Level-2 data in RTN coordinates. Release of daily plots in RTN coordinates at same time. The data on several days has a low-level noise of undetermined source. It may be an interplanetary source, or it may not. Those days are day 358 of 2003 and days 56, 57 of 2004. It also observed on day 77 of 2004 which will be releases shortly. The noise is most evident in the |B| when |B| is otherwise very steady and the component fluctuations are low. This is not the first time this signal has been detected, but with solar minimum it may become more evident. --- CWS