This record describes SVP data collected on RV Investigator voyage IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories", which departed Darwin on September 30 and returned to Fremantle on November 3, 2022. This was a continuation of voyage IN2021_v04. A total of 44 SVP casts were conducted over the duration of this voyage using the Valeport MIDAS SVX2 sound velocity profiler, with 5 casts considered as failed due to low battery issues (i.e. SVX2_009, 010, 023, 027 & 037). This instrument was attached to the CTD frame and deployed with the CTD casts, therefore SVP & CTD share common deployment cast numbers. Data are stored in ASCII format files with extention *.000 at CSIRO. Additional information regarding this dataset is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes magnetometer data collected on RV Investigator voyage IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories", which departed Darwin on September 30 and returned to Fremantle on November 3, 2022. This was a continuation of voyage IN2021_v04. The SeaSPY2 magnetometer uses an omnidirectional Overhauser sensor that requires no realignment or recalibration and has no heading error. The instrument has an absolute accuracy of 0.1 nT, sensor sensitivity of 0.01 nT and resolution of 0.001 nT. Data are stored in .CSV and .MMS data files at CSIRO. 92 MB of raw data was acquired in this dataset. No processing has been conducted on this data. The magnetometer was towed ~300 m astern of the ship and a layback value of 361 was applied to the magnetometer data. This was the total distance behind the ship's positioning reference point. Additional information regarding this dataset is contained in the GSM data acquisition and processing report.

This record describes XBT data collected on RV Investigator voyage IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories", which departed Darwin on September 30 and returned to Fremantle on November 3, 2022. This was a continuation of voyage IN2021_v04. A total of 13 XBT casts were conducted over the duration of this voyage (12 successful and 1 failed drop). Data are stored in netCDF files at CSIRO. Additional information regarding this dataset 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 IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories" which departed Darwin on September 30 and returned to Fremantle November 3, 2022. This was a continuation of voyage IN2021_v04. The Kongsberg EM710 MKII multibeam echosounder was used to acquire seafloor bathymetry and backscatter information and watercolumn backscatter between Darwin and Fremantle (via the Indian Ocean Territories) in areas with water depths shallower than ~1000m. 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. During this voyage, the frequency range was set to 70 to 100 kHz. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 138 *.all files totaling 32.6 GB of raw bathymetry/backscatter data and 135 *.wcd files totaling 233 GB of 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. GPS tide was computed using the EGM2008 model and applied to the processed data. Processed data has had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry 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 IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories", which departed Darwin on September 30 and returned to Fremantle on November 3, 2022. This was a continuation of voyage IN2021_v04. The Kongsberg EM122 multibeam echosounder was used to acquire seafloor bathymetry, backscatter information and watercolumn backscatter between Darwin and Fremantle (via the Indian Ocean Territories). 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 1195 *.all files totaling 54 GB of raw bathymetry/backscatter data and 1195 *.wcd files totaling 73.7 GB of 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. GPS tide was computed using the EGM2008 model and 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 scientific split-beam echosounder data collected on the RV Investigator voyage IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories" which departed Darwin on September 30 and returned to Fremantle on November 3, 2022. This was a continuation of voyage IN2021_v04. The Simrad EK60 split beam echosounders for 18 kHz and Simrad EK80 split beam echosounders for 38, 70 120, 200 and 333 kHz were used to acquire acoustic backscatter data to a range of 250 m (shallow water) or 1500 m (deep water) between Darwin and Fremantle. All frequencies were logged continuously for the extent of the voyage, except on occasion around Cocos (Keeling) Island and Muirfield Seamount when the 70 and 120 kHz frequencies were set to passive to avoid interference with the EM710 when conducting shallow multibeam bathymetry surveys. Data are stored in *.raw, *.bot and *.idx format at CSIRO. There are 2138 files totalling 149 GB of raw data in this dataset. Additional information regarding this dataset is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes sub bottom profiler data collected on RV Investigator voyage voyage IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories", which departed Darwin on September 30 and returned to Fremantle on November 3, 2022. This was a continuation of voyage IN2021_v04. The Kongsberg SBP120 (sub bottom profiler) was used to acquire data containing the specular reflections at different sediment interfaces below the seafloor. The SBP120 provides a 3° by 3° angular resolution. The echosounder's frequency sweep range is from 2.5 to 7 kHz. With the exception of periods when stationary (e.g. during CTD casts), the SBP120 was logged continuously for the extent of the voyage. Data are stored in *.raw (1015 files 22.2 GB) raw and *.seg (1006 files 22.1 GB) segy formats at CSIRO. The segy format data had a real time processing stream applied, which applies gain, a gain correction, and matched filter with replica shaping. Additional information regarding this dataset is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes gravity data collected on RV Investigator voyage IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories", which departed Darwin on September 30 and returned to Fremantle on November 3, 2022. This was a continuation of voyage IN2021_v04. The gravity meter instrument is a MicroG Lacoste Air-Sea II. Data are stored in .ENV and .DAT data files at CSIRO. There are 36 files totalling 576 MB of raw data in this dataset. A wharf tie was undertaken at the end of the voyage at Henderson Wharf (in Fremantle) upon vessel arrival using a Scintrex Autograv CG-5. No wharf could be undertaken in Darwin due to personnel restrictions. Note: Due to a Time Server issue on the Gravity PC, data from Julian days 273-297 (i.e. 30th September to 24th October 2022) had to be time corrected, and those files can be found in the "time_corrected" folder which is stored with the raw data. Wharf tie data can be found in "Henderson_wharf_tie_2022_11_03.TXT", which is stored with the raw data. No processing has been conducted on this data. Additional information regarding this dataset is contained in the GSM data acquisition and processing report.

This record describes the Acoustic Doppler Current Profiler (ADCP) data collected from the Marine National Facility RV Investigator voyage IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories." The voyage took place between September 30, 2022 (ACST) and November 3, 2022 (AWST), departing from Darwin and returning to Fremantle. As required, one or both ADCPs were turned off in less than 500 m depths to avoid the significant acoustic interference these systems generate, particularly between the OS75 and EM710. Changes to the ADCPs were logged and DAP were informed when multibeam bathymetry was considered a scientific priority. The OS75 was switched off for significant parts of the voyage, especially around Christmas and Cocos (Keeling) Islands while shallow water mapping was being undertaken. Throughout the voyage there were high counts of low-quality position data from Seapath. In collaboration with UHDAS Support, on the 2022-10-10 the ADCP was configured to use POSMV rather than Seapath for position and heading data, consequently the data has been split into two parts. ADCP data were collected using the University of Hawaii Data Acquisition System (UHDAS) and post-processed using the Common Ocean Data Access System (CODAS). Documentation for these systems can be found here: https://currents.soest.hawaii.edu/docs/adcp_doc. Both the RDI Ocean Surveyor 150kHz ADCP and the RDI Ocean Surveyor 75kHz ADCP were run in narrowband mode. The OS150 ADCP was used throughout the voyage. The OS75 was used in deep waters and turned off in shallower waters so as not to interfere with the EM710 Internal triggering was used. The drop keel was at 8 m 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 (quality-controlled), and then archived by the CSIRO National Collections and Marine Infrastructure (NCMI) Information and Data Centre (IDC).

This record describes Hydrology (HYD) data collected from the Marine National Facility (MNF) RV Investigator voyage: IN2022_V08, titled "Biodiversity Assessment of Australia’s Indian Ocean Territories." The voyage took place between September 30, 2022 (ACST) and November 3, 2022 (AWST), departing from Darwin and returning to Fremantle. Hydrology samples were collected from Niskin bottles sampled at various depths during Conductivity-Temperature-Depth (CTD) deployments. Parameters analysed were salinity, dissolved oxygen, phosphate, silicate, nitrate plus nitrite and ammonium. This dataset has been processed (quality-controlled), and 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.