Temperature and Wind Sensor for InSight (TWINS)
              Pressure Sensor (PS)










    On this page

    Introduction
    Data Acquisition and Structure
    Selecting Data
    Citing datasets for publication
    Bibliography
    Spice

    INSIGHT
    Credit JPL/NASA






























    Introduction

    InSight landed on Mars on November 26, 2018. The goal of the mission is to study the deep interior. The primary phase of the mission is scheduled to extend for a little more than a Martian year. The main components of the instrument package are the Seismic Experiment for Interior Structure (SEIS) and the Heat-Flow and Physical Properties Probe (HP3). They are supported by the Auxiliary Payload Sensor Subsystem (APSS), which includes temperature, wind (this page) and pressure sensors (this page) and a magnetometer to support of SEIS. A radiometer to measure surface temperature and thermal properties supports HP3. X-band radio science, Rotation and Interior Structure Experiment (RISE), will refine knowledge concerning global structure. The Instrument Deployment Camera (IDC) and the Instrument Context Camera (ICC) provide support imaging.

    The fact that the InSight instrument ensemble contains a highly sensitive pressure sensor (PS), and temperature and wind detectors (TWINS), combined with the radiometer (RAD) instrument, which will measure the surface brightness temperature, and a camera with multiple filters (IDC), which can be used to quantify atmospheric opacity, provides the components for an effective weather station. This weather station provides a more continuous and higher-frequency record of pressure, air temperature and winds at the surface of Mars than previous in situ missions.

    A summary of the mission, spacecraft and instruments is available.

    References



    Spiga, A., Banfield, D., Teanby, N.A. et al. Atmospheric Science with InSIght, Space Sci Rev (2018) 214: 109. https://doi.org/10.1007/s11214-018-0543-0

    Banfield,D., et al., InSight Auxiliary Payload Sensor Suite (APSS), Space Sci Rev (2019) 215: 4. https://doi.org/10.1007/s11214-018-0570-x



    Instrument Description

    The Temperature and Wind for InSight (TWINS) instrument and Pressure Sensor (PS) are part of the APSS. Data from both TWINS and PS will be used by SEIS to reduce and decorrelate atmospheric effects from seismic signals.

    TWINS is comprised of two identical booms arrayed with wind and temperature sensors that are placed on diametrically opposite sides of the lander deck, one pointing in the -Y lander axis direction and the other in the +Y direction. The booms are approximately 1.4m above the ground level, 200mm above the lander top deck, horizontally placed, and in parallel to each other. See the software specifications document (pdf) Section 2.6.1.

    PS is a pressure transducer located in the lander body, and connected to the ambient atmosphere with an inlet on the lander top deck. See the software specifications document (pdf) Section 2.6.2.






    INSIGHT
    An Example of TWINS and PS Data. The barbs extending from each wind speed data point indicate the compass direction of the wind, with each half flag representing approximately 2.5 meters per second. A circle in place of a barb indicates a wind speed less than 2.5 meters per second. Credit: NASA/JPL-Caltech/Cornell/CAB











































    Data Acquisition
    Twins

    During the deployment phase TWINS provided data regarding temperature and wind speed and direction, with the objective of assessing when to deploy instruments. Both booms were used, limited by available resources.

    Continuous logging is the main driver for TWINS operation. Available transmission bandwidth per sol will dictate what portion of the recorded data can be downloaded to Earth. Two retrieval modes are defined: event retrieval mode. (high sampling rate) and continuous mode. In continuous mode, only selected, low frequency data are sent. So far, during the science-monitoring phase, both booms have been used and as long as the earlier downlink rate is available this will be the case. The continuous mode will be sampled less, both booms will be used and the continuous mode will be the dominant mode of operation.

    Event retrieval is very dependent of available downlink bandwidth, and most of the data will be in continuous mode.


    Table 1 summarizes downlink modes. So far as of May 2019, available downlink has allowed the event retrieval mode to be the dominate mode.

    Table 1 TWINS Downlink Modes
    Downlink ModeWind speed data retrievalAir Temperature data retrievalAdditional
    Continuous1/M HzN samples average and standard deviation at 1/M HzM*=decimation rate=20, 10, 2, 1
    N**=average window=7
    Event/Full1 Hz, 0.5Hz, 02.Hz1 Hz, 0.5Hz, 0.2Hz   


    *For nominal operations, M is set to 10. Since TWINS has a sampling rate of 1Hz, this makes an effective frequency of 0.1Hz.
    **a running average and standard deviation of the last N samples is transmitted

    PS

    Because the pressure decorrelation is crucial to interpreting the seismic signals, pressure data are needed at all times of the mission, the pressure sensor is designed to operate constantly throughout the mission, only being turned off in case of low power availability. The native sampling rate on board the lander is 20 Hz, but is downsampled to a lower rate continuous data stream. For the nominal downlink case (continuous mode, ~38 Mbits/Sol), the pressure sensor will return continuous data downsampled to 2 Hz, and its temperature sensor will be downsampled to 0.2 Hz. There will be a certain amount of the downlink budget allocated to “events” which will be special times in the mission where anomalous signals are detected in the pressure (or seismic or wind or magnetic) data sets, and full temporal resolution data sets are desired. In this case, a higher rate data set from the pressure sensor will be downlinked.

    Pressure Sensor continuous and event modes data rates may change during the mission. Table 2 summarizes rates defined at the writing of this document.

    Table 2 Pressure Downlink Modes
    Downlink ModePressure data retrievalTemperature data retrievalAdditional
    Continuous2 Hz, 10 Hz0.2 HzRMS of >1Hz@0.5 Hz or 1Hz
    Event10 Hz, 5Hz, 4Hz10 Hz, 5Hz, 4Hz, 2Hz, 1Hz, 0.5Hz   
    Full20 Hz20 Hz   


    Selecting Data Individual data files for both TWINS and PS data span 1 SOL = 24 hr 39 min and 35.244 sec.


    Data Set Description - SIS (pdf)

    Calibrated Data


    Selected data can be retrieved in 2 ways
    1) Downloading an index, selecting components and uploading your selection.
    Indices that tabulate information associated with each product are available.

    a. Select your index
    b. Sort and make your selection
    c. Upload the URN values from your revised index (note the total uncompressed file size before requesting)

    2) Selecting specific parameters and requesting limited data files (Coming Soon)


    Raw Data - The data files are in ASCII format and the data is in counts.


    Downloading annual collections of data
    2019 TWINS
    2019 PS

    Citing datasets for publication


    Rodriguez-Manfredi, J.A. et al., InSight APSS TWINS Data Product Bundle, urn:nasa:pds:insight_twins, 2019.

    Banfield, D. et al., InSight APSS PS Data Product Bundle, urn:nasa:pds:insight_ps, 2019.

    Bibliography - A listing of team members to facilitate literature searches



    Spice - Archived Juno SPICE ancillary data providing observation geometry (positions, orientations, instrument pointing, time conversions, etc.) are available from the PDS NAIF Node.