Pre-processing

Overview

In terms of data processing, the HFI ground segment handles two types of data, both made available via the MOC:

• packet data transmitted from the satellite. These come from the different subsystems of the SVM, from the Sorption Cooler and from the 2 instruments. The packets come in Near Real Time during the DTCP or are dumped to the ground, consolidated by and stored at MOC.
• auxiliary data. These are data produced by MOC. The only 3 products used by the HFI DPC are the pointing data, the orbit data, and the time correlation with UTC.

All data are retrieved by the HFI DPC level 1 software and stored in the HFI DPC database.

Raw data ingestion

Housekeeping parameters

For several reasons (systems monitoring, potential impact of the environment, understanding of the bolometer data), the HFI DPC gathers and stores in its database the satellite subsystems housekeeping parameters:

• Command and Data Management System
• Attitude Control & Measurement Subsystem
• Thermal Control System
• Sorption Cooler System
• HFI housekeeping parameters

The structure and the frequency of the packets built by these subsystems and the format of the house keeping parameters are described in the Mission Information Bases [refer to an hypothetical MIB section under MOC responsibility]. The HFI L1 software uses these MIBs to extract the house keeping parameters from the packets. Given the status of each subsystem, the parameters are gathered in the HFI database in groups. The HFI L1 software builds in each group a vector of time (usually named TIMESEC) and a single vector per housekeeping parameter.

Bolometer data

The HFI science data is retrieved and reconstructed as described in section 3.1 of the Early DPC paper [reference].

Pointing interpolation

The pointing data are built by the MOC Flight Dynamics team. The pointing data are made available to the DPC via AHF files [refer to the AHF structure and to the PLA AHF folders]. All data in the AHF files are ingested in the HFI database. They’re then interpolated to the bolometer frequency [refer to the Karim’s section].

Orbit data ingestion

Satellite orbit data are built by the MOC Flight Dynamics team. The orbit data are made available to the DPC via orbit files [refer to the orbit ICD and to the appropriate PLA folders] and are ingested in the HFI database . These same data are also ingested into the NASA Horizons system [refer to the URL], under ESA’s responsibility. The use of the orbit data is two-fold: they are used compute the CMB orbital dipole [refer to the L2 appropriate section] and to compute the positions of solar system objects [refer to the L2 appropriate section].

Time correlation data ingestion

The MOC is responsible for providing information about the relationship between the satellite On Board Time (OBT) and Universal Coded Time (UTC) [refer to a hypothetical Time Management section]. This information comes via several measurements of OBT and UTC pairs each day, measured during the satellite ranging [refer to the ICD and to the appropriate PLA folders]. An order 3 polynomial is then fitted to the data [refer to the appropriate L2 section]. As the whole HFI data management and processing uses uses OBT, the OBT-UTC correlation is only used when importing orbit data from Horizons.

Some statistics on the raw data

-	From launch to the end of full mission	Scientific full mission
Number of days	974 days	884 days
Number of HFI packets generated onboard (HSK/science)
Number of HFI packets generated onboard (HSK/science)
Number of HFI packets lost on board (HSK/science)
Number of HFI packets lost on ground (HSK/science)
Number of retreived HFI packets (HSK/science)
Number of missing raw data packets/samples (HSK/science)
Number of data raw data samples stored in the database (HSK/science)
Number of different housekeeping parameters stored in the database (HFI/SCS/sat)
Number of pointing samples stored in the database