From 40cf2882410984600de8095776767c65f5d5a8a4 Mon Sep 17 00:00:00 2001 From: Elena.Budnik Date: Thu, 22 Dec 2016 10:41:01 +0100 Subject: [PATCH] caveats added to MAVEN/MAG --- NumericalData/AMDA/MAVEN/MAG/mav-mag-all.xml | 11 +++-------- NumericalData/AMDA/MAVEN/MAG/mav-mag-pds.xml | 32 +++++++++++++++++++++++++++++++- 2 files changed, 34 insertions(+), 9 deletions(-) diff --git a/NumericalData/AMDA/MAVEN/MAG/mav-mag-all.xml b/NumericalData/AMDA/MAVEN/MAG/mav-mag-all.xml index a2c462f..b25972f 100644 --- a/NumericalData/AMDA/MAVEN/MAG/mav-mag-all.xml +++ b/NumericalData/AMDA/MAVEN/MAG/mav-mag-all.xml @@ -5,18 +5,13 @@ spase://CDPP/NumericalData/AMDA/MAVEN/MAG/mav-mag-all 1 sec - 2015-10-12T10:48:29Z - averged over 1 sec - + 2016-12-12T10:48:29Z + averged over 1 sec from high resolution PDS data Principal Investigator : John E.P. Connerney, NASA GODDARD, Greenbelt spase://CDPP/Person/John.E.P.Connerney PrincipalInvestigator - - - spase://CDPP/Person/Elena.Budnik - TechnicalContact - + MAG web page, Summary sheet http://lasp.colorado.edu/home/maven/science/instrument-package/mag/ diff --git a/NumericalData/AMDA/MAVEN/MAG/mav-mag-pds.xml b/NumericalData/AMDA/MAVEN/MAG/mav-mag-pds.xml index 201e6f1..29f087d 100644 --- a/NumericalData/AMDA/MAVEN/MAG/mav-mag-pds.xml +++ b/NumericalData/AMDA/MAVEN/MAG/mav-mag-pds.xml @@ -53,7 +53,37 @@ PT0.031S Mars - + MAG data products are provided in several useful coordinate systems and at the highest time resolution +available. The MAG observations contain some known artifacts that you may encounter in your use of the +data that you should be aware of. These are related to several different sources on the spacecraft that have +been, and continue to be, under investigation. This message is dated April 10, 2015, and it represents +our current (and evolving) understanding of the status of the spacecraft and its influence on MAG +data. These include: +* rapid magnetic field variations of ~6 nT in magnitude (in spacecraft payload coordinate axes y and z) +associated with infrequent thruster firings (every few days) that are employed in trajectory correction +maneuvers (TCM). These are relatively easy to identify. +* variations (in spacecraft payload coordinate axes y and z) of ~1 nT in magnitude associated with solar +array currents in circuits at the outer edge of the solar arrays, near the magnetometer sensor. MAG +processing mitigates these signatures where spacecraft engineering telemetry is available at high time +resolution. The necessary spacecraft engineering data was made available after Jan 9, 2015, following in- +flight spacecraft testing to isolate the problem. Prior to this time, we use a coarse indication of solar array +currents to correct the data, and this correction will be out of time step with the actual needed correction +part of the time. Corrections applied are listed on each record along with the corrected data. These +variations may appear as step functions, e.g., when the spacecraft enters eclipse, or slow variations as the +spacecraft attitude with respect to the sun varies. They were identified in the quiet, weak field +environment of cruise and when illumination on the solar arrays was more intense than experienced in +cruise. +* multiple sinewave variations usually of ~0.1 nT in magnitude, that track the frequency of operation of +the four Reaction Wheel Assemblies (RWAs). The magnitude of these variations has been observed to +increase substantially when the RWAs are operated at very low frequencies; at such times they may +appear prominently in spectra of MAG observations. +* the "static" or slowly-varying spacecraft field has been estimated using spacecraft roll maneuvers that +are scheduled to occur approximately every 2 months. The MAVEN static sc field specification was NTE +2 nT. The MAG data processed for December 2014 use an estimate of the spacecraft field obtained from +the day 353 2014 magroll maneuvers, the only set performed subsequent to deployment of the APP after +insertion into Mars orbit. We have yet to verify if this sc field estimate remains relatively constant or if it +varies over the interval between magroll maneuvers. Investigation of the time variability of this part of the +sc field is expected shortly. b_mso -- libgit2 0.21.2