PARKER SOLAR PROBE Attitude and Ephemeris Data (CDF)
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This data sets contains spacecraft attitude (roll and offpointing from SPICE kernels), distance from Sun in AU and RTN coordinates. The RTN frame is defined as follows : R axis points from the Sun to the spacecraft. T = Omega x R, where Omega is the Sun's rotation axis. N = R x T. The XYZ or spacecraft frame (also referred to as SC) is defined as follows for Parker Solar Probe : Z axis corresponds to the satellite axis (and its arm) and points towards the Sun. When PSP is facing the Sun, Z = -R. X is normally included in the ecliptic plane, with X = Z x Omega, when PSP is facing the Sun. Y is normally perpendicular to the ecliptic plane, pointing towards the South. PSP's solar panels are oriented along the Y axis. The data file with position is in CDF format. Records are arranged chronologically, with 1 min time resolution. One record contains : Epoch (Y-m-d H:M:S.000000000 format), cos_roll, cos_offpointing, rad_AU (AU), R value (m), T value (m), N value (m) with : Epoch : Time of the record in TT2000 format, exactly in the kernels. This time corresponds to nanoseconds since 1 Jan 2000 12:00:00 with leap seconds included. cos_roll : Cosine of roll angle, i.e. angle between X and T axis (from (XYZ) and (RTN) frames). This angle mainly varies during satellite roll operations, which are carried out several times per orbit to calibrate the MAG fluxgates. cos_offpointing : Cosine of offpointing angle, i.e. angle between Z and R axis. This angle is important for determining when the instruments on the boom are sunlit. Off-pointing primarily occurs when the spacecraft is away from the Sun. rad_AU : Parker Solar Probe-Sun distance in AU. R, T and N values (in m) of Parker Solar Probe in (RTN) frame. Attitude data, PSP-Sun distance and PSP ephemeris are computed from SPICE kernels (see the CDAWEB Data Center https://cdaweb.gsfc.nasa.gov/pub/data/psp/ephemeris/spice/).
本数据集包含航天器姿态（侧滚角及相对于SPICE内核（SPICE kernels）的偏航偏离角）、以天文单位（AU）计量的日心距离，以及RTN坐标系（RTN frame）下的坐标值。RTN坐标系定义如下：R轴由太阳指向航天器；T = Ω × R，其中Ω为太阳自转轴；N = R × T。针对帕克太阳探测器（Parker Solar Probe, PSP），其XYZ本体坐标系（亦称SC坐标系）定义为：Z轴对应卫星本体轴（及其伸展臂），指向太阳。当PSP正对太阳时，Z = -R。X轴通常位于黄道面内，当PSP正对太阳时，X = Z × Ω。Y轴通常垂直于黄道面，指向南天极。PSP的太阳能电池板沿Y轴定向。 本数据集的位置数据采用CDF格式（CDF format）存储，记录按时间顺序排列，时间分辨率为1分钟。单条记录包含以下字段：纪元（Epoch，格式为Y-m-d H:M:S.000000000）、cos_roll、cos_offpointing、rad_AU（单位：AU）、R值（单位：米）、T值（单位：米）、N值（单位：米），各字段说明如下： 1. Epoch（纪元）：采用TT2000格式的记录时刻，与内核中的记录完全一致。该时刻对应自2000年1月1日12:00:00起的纳秒数，已计入闰秒。 2. cos_roll：侧滚角的余弦值，即本体坐标系X轴与RTN坐标系T轴之间的夹角。该角度主要在卫星侧滚操作期间发生变化，PSP每条轨道会多次执行此类操作以校准磁强计（MAG）的磁通门传感器。 3. cos_offpointing：偏航偏离角的余弦值，即本体坐标系Z轴与RTN坐标系R轴之间的夹角。该参数可用于判断伸展臂上的载荷是否处于太阳直射区域。偏航偏离主要发生在航天器远离太阳时。 4. rad_AU：帕克太阳探测器与太阳之间的距离，单位为天文单位（AU）。 5. R、T、N：帕克太阳探测器在RTN坐标系下的坐标值，单位为米。 本数据集的姿态数据、PSP与太阳的距离以及PSP星历均通过SPICE内核计算得到，数据来源为CDAWEB数据中心：https://cdaweb.gsfc.nasa.gov/pub/data/psp/ephemeris/spice/。
