This record describes multibeam echosounder data collected on RV Investigator voyage IN2021_V04 (Biodiversity Assessment of Australia’s Indian Ocean Territories), which departed Darwin on the 30th June 2021 and returned to Hobart on the 29th July 2021. The Kongsberg EM710 MKII multibeam echosounder was used to acquire seafloor bathymetry and backscatter information and watercolumn backscatter between Darwin and Scott Reef (Northern Territory), south west shelf of Western Australia and on the south west shelf of Tasmania. The EM710 MKII provides a 0.5° by 1° transmit and receive angular resolution respectively. The echosounder's nominal frequency range is from 40 to 100 kHz. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 94 files totalling 22.6 GB of raw bathymetry and backscatter data, and 94 files totalling 166 GB of raw watercolumn data in this dataset. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position. The data have been reduced to approximate Mean Sea Level (MSL) using the Earth Gravitation Model 2008 (EGM2008) 1 arc-minute grid. Tide corrections were not applied to the processed data. Processed data has had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry and backscatter grids in geotiff format. Additional information regarding this dataset, including further information on processing streams, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes multibeam echosounder data collected on RV Investigator voyage IN2021_V04 (Biodiversity Assessment of Australia’s Indian Ocean Territories), which departed Darwin on the 30th June 2021 and returned to Hobart on the 29th July 2021. The Kongsberg EM122 multibeam echosounder was used to acquire seafloor bathymetry, backscatter information and watercolumn backscatter between Scott Reef (Northern Territory) and south west shelf of Tasmania. The EM122 provides a 1 degree by 1 degree angular resolution. The echosounder's nominal frequency is 12 kHz. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 715 files totalling 43.2 GB of raw bathymetry & backscatter data, and 715 files totalling 60.3 GB of raw watercolumn data in this dataset.. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position. The data have been reduced to approximate Mean Sea Level (MSL) using the Earth Gravitation Model 2008 (EGM2008) 1 arc-minute grid. Tide corrections were not applied to the processed data. Processed data had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry and backscatter grids in geotiff format. Additional information regarding this dataset, including information on processing streams, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes the Acoustic Doppler Current Profiler (ADCP) data collected from the Marine National Facility RV Investigator voyage IN2021_V04, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories." The voyage took place between June 30 and July 29, 2021 departing from Darwin (NT) and returning in Hobart (TAS). Data was collected during in2021_v04 for most of the voyage. The OS75 was turned off whilst in shallower water to prioritise mapping and the OS150 was turned off briefly for mapping around Christmas Island. Data was collected using UHDAS and post-processed using CODAS. Both the RDI Ocean Surveyor 150kHz ADCP and the RDI Ocean Surveyor 75kHz ADCP were run in narrowband. Internal triggering was used. The drop keel was at 2m below the waterline for the duration of the voyage. See the voyage computing and electronics report for more details regarding data acquisition. This dataset was processed and then archived within the CSIRO National Collections and Marine Infrastructure (NCMI) Information and Data Centre (IDC) in Hobart.

This record describes Hydrology (HYD) data collected from the Marine National Facility (MNF) RV Investigator voyage IN2021_V04, titled: "Biodiversity Assessment of Australia’s Indian Ocean Territories." The voyage took place between June 30 and July 29, 2021 departing from Darwin (NT) and arriving in Hobart (TAS). Water samples collected during the voyage were analysed in the ship’s hydrochemistry laboratory for nutrients, dissolved oxygen, and salinity. Five nutrients were determined: silicate (Si(OH)4), phosphate (PO4), nitrate + nitrite (NOx), nitrite (NO2) and ammonium (NH4). Certified reference materials for nutrients in seawater (RMNS) were within 3% of their certified values. See table for the CTD deployment versus measured RMNS values. Final hydrology data, analytical methods, related log sheets and processing notes can be obtained from the CSIRO data centre. This dataset has been archived at the CSIRO National Collections and Marine Infrastructure (NCMI) Information and Data Centre (IDC) in Hobart. Additional information regarding this dataset is contained in the Voyage Report and Data Processing Report.

This record describes the Conductivity-Temperature-Depth (CTD) data collected from the Marine National Facility RV Investigator voyage IN2021_V04, titled: "Biodiversity Assessment of Australia’s Indian Ocean Territories." The voyage took place between June 30 and July 29, 2021 departing from Darwin (NT) and arriving in Hobart (TAS). Data for 25 deployments were acquired using the Sea-Bird SBE911 CTD 24, fitted with 31 twelve litre bottles on the rosette sampler. Sea-Bird-supplied calibration factors were used to compute the pressures and preliminary conductivity values. CSIRO -supplied calibrations were applied to the temperature data. The data were subjected to automated QC to remove spikes and out-of-range values. The final conductivity calibration was based on a single deployment grouping. The final calibration from the primary sensor had a standard deviation (SD) of 0.0013062 PSU, within our target of ‘better than 0.002 PSU’. The standard product of 1 decibar binned averaged were produced using data from the primary sensors. The dissolved oxygen data calibration fit had a SD of 0.089089μM. The agreement between the CTD and bottle data was good. There was an observed spike in values indicating a blockage in the secondary sensors of CTD deployment 11 around 2700 decibar and it is recommended to use the primary sensor data. An Altimeter, Nephelometer, Transmissometer, CDOM, Fluorometer, and Turbidity meter were also installed on the auxiliary A/D channels of the CTD. The Seapoint nephelometer values were found to be out of the expected range for the sensor. The collected data were subsequently processed and archived within the CSIRO National Collections and Marine Infrastructure (NCMI) Information and Data Centre (IDC) in Hobart. Additional information regarding this dataset may be contained in the Voyage Summary and the CTD Data Processing Report.

This record describes the Underway (UWY) data collected from the Marine National Facility (MNF) RV Investigator Voyage IN2021_V04, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories." The voyage took place between June 30 and July 29, 2021 departing from Darwin (NT) and arriving in Hobart (TAS). Standard Underway data is continuously recorded, consisting of: (1) Navigation data (NAV): Latitude, Longitude, Speed, Heading, Course Over Ground, Gyros, and Doppler Log (dual GPS instrument). (2) Thermosalinograph (TSG): Water Salinity, Flow-Rate, Temperature, Fluorescence, pCO2 and Optode/Oxygen. (3) Atmospheric (MET): Humidity, Wind Speed and Direction (vane and ultrasonic), Radiometer/Sea Surface Temperature, Pyranometer/Solar Radiation, Photosynthetically Active Radiation (PAR), Air Temperature, Air Pressure, Rain, Ozone and Trace Gases (port and starboard instruments). The quality-controlled RV Investigator underway meteorological and SST data are supplied to the IMOS AODN where they are publicly available at the "Ships of Opportunity" Thredds server (http://thredds.aodn.org.au/thredds/catalog/IMOS/SOOP/SOOP-ASF/VLMJ_Investigator/catalog.html) for research. From there, they are downloaded by NOAA for their In Situ Quality Monitoring web site (iQUAM2) and made available for satellite SST validation. The SBE 38 SST data are used within the Australian Bureau of Meteorology for real-time satellite SST validation and ingested into real-time SST analyses which are then used as the boundary condition for Numerical Weather Prediction models. The meteorological and SST data are uploaded onto the Global Telecommunications System (GTS) for global dissemination to Meteorological Agencies, and separately supplied to the SAMOS (http://samos.coaps.fsu.edu/html/) Project for air-sea flux research. The real-time SBE 38 SST data are currently (2017) used in the following data products (accessed via the GTS): • International Comprehensive Ocean-Atmosphere Data Set (ICOADS R3.0) (http://icoads.noaa.gov/) • NOAA NCEI Extended Reconstructed Sea Surface Temperature version 4 (ERSST.v4) (https://www.ncdc.noaa.gov/data-access/marineocean-data/extended-reconstructed-sea-surface-temperature-ersst-v4) • Hadley Centre SST Data Set (HadSST3) (http://www.metoffice.gov.uk/hadobs/hadsst3/) • Global Ocean Surface Underway Data (GOSUD) Project (http://www.gosud.org/) • Bureau of Meteorology daily and weekly SST analyses (http://www.bom.gov.au/marine/sst.shtml) • NOAA NCEI “Reynolds” daily global OISST analysis (https://www.ncdc.noaa.gov/oisst) • NASA JPL “MUR” 1 km daily global SST analysis (https://mur.jpl.nasa.gov/) • UK Met Office “OSTIA” daily global SST analysis (http://ghrsst-pp.metoffice.com/pages/latest_analysis/ostia.html) • CMC daily global SST analysis • Ourocean “G1SST” global daily 1 km SST analysis (https://ourocean.jpl.nasa.gov/SST) As part of the underway data gathering system, other datasets are produced (e.g., pCO2, ISAR SST) which are processed separately and have their own metadata records. Data are recorded at 5 second intervals. Near real-time data are available via the link "Visualisation tool for Underway Data." This dataset has been processed and archived within the CSIRO National Collections and Marine Infrastructure (NCMI) Information and Data Centre (IDC) in Hobart (TAS). Data are available at time intervals of 5 sec (NetCDF format), 10 sec and 5 min (ASCII format). Additional information regarding this dataset is contained in the Voyage Summary and/or the Data Processing Report for this voyage.

This record describes the End of Voyage (EOV) data archive from the Marine National Facility (MNF) RV Investigator voyage IN2021_V04, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories (IOT)." The voyage took place from Darwin (NT) to Hobart (TAS) between June 30 and July 29, 2021 (AEST). Piggy-back project: "Exploring the genomics of convergent snout elongations in deep-sea fishes." For further information please refer to the voyage documentation links. Instruments used and data collected include: Regular measurements: Lowered ADCP (LADCP), Acoustic Doppler Current Profiler (ADCP; 75, 150 KHz ), Greenhouse Gas Analysers (Picarro), Cloud Condensation Nuclei counter (CCN), Condensation Particle Counters (CPC), Disdrometer, Radon sensor, Scanning Mobility Particle Sizers (SMPS), CTD, Hydrochemistry, Fisheries Echosounder (EK80), Multibeam Echosounder (EM710, EM122), Sub-bottom Profiler (SBP120), GPS Positioning System, Doppler Velocity Log, Thermosalinographs (TSG), Fluorometer, Oxygen Optode, Infrared Sea Surface Temperature Autonomous Radiometer (ISAR), pCO2, Gravimeter, Multiangle Absorption Photometer (MAAP), Ozone Sensor, Nephelometer, Atmospheric Temperature, Humidity, Pressure, Wind and Rain sensors, Photosynthetically Active Radiation (PAR) sensor, Precision Infrared Radiometer (PIR), Precision Spectral Pyranometer (PSP), Starboard and Portside Radiometers, Air Sampler, Ultra Short BaseLine Underwater Positioning System (USBL), Weather Radar, Expendable Bathythermographs (XBTs). Voyage-specific measurements: Deep Towed Camera (DTC), Specimen Images, Beam Trawl, Surface Net, Microbial Samples, Rock Dredge, Sediment Grab. The archive for the IN2021_V04 EOV raw data is curated by the CSIRO National Collections and Marine Infrastructure (NCMI) Information and Data Centre (IDC) in Hobart, with a permanent archive at the CSIRO Data Access Portal (DAP, https://data.csiro.au/dap/), providing access to voyage participants and processors of the data collected on the voyage. All voyage documentation is available electronically to MNF support via the local network. Access to voyage documentation for non-CSIRO participants can be made via NCMI_DataLibrarians@csiro.au.