What was the purpose of CryoVEx 2019?
The ESA CryoVEx/ICESat‐2 summer campaign 2019 is an add‐on to the campaign carried out in the spring 2019, which did not cover all the flights that were planned due to weather obstacles. .
The aims of this campaign were to:
- Cross‐validating ESA CryoSat‐2 and NASA ICESat‐2 missions over summer sea ice in the Arctic
- Test a dual‐frequency (Ka/Ku‐band) airborne radar system developed and operated by Center for Remote Sensing of Ice Sheets (CReSIS), University of Kansas.
This is done to exploit the concept for future polar satellite missions, i.e. the CRISTAL mission. The campaign involved operations of the CReSIS Ka/Ku‐band radar system, and the DTU laser scanner setup using chartered Twin Otter aircraft (TF‐POF) from Norlandair, Iceland. This instrument setup differs from previous CryoVEx campaigns (i.e. CryoVEx/KAREN 2016 fall and 2017 spring campaigns, CryoVEx/Antarctic 2017‐18 campaign and CryoVEx/ICESat‐2 2019 spring campaign), where the Ka‐ band and Ku‐band airborne radar altimeters were independent instruments, i.e. the MetaSensing Ka‐ band radar (KAREN) and ESA’s Ku‐band radar (ASIRAS).
Two sea ice flights were flown in the Arctic Ocean out of Station Nord including two near coincident underflights of ICESat‐2 and two of CryoSat‐2. Transit flights crossing the Greenland Ice Sheet were also used to collect measurements when possible, following flight lines that have been surveyed before. The airborne campaign was carried out during August 6 – August 16, 2019. The campaign was coordinated by National Space Institute, Technical University of Denmark (DTU Space) in collaboration with CReSIS, University of Kansas, US.
What was the outcome of CryoVEx 2019?
First results of the CReSIS radar demonstrates that the system has sufficient sensitivity to conduct dual‐band altimetry measurements to capture specular returns, i.e. leads and melt ponds over sea ice covered regions.
The CReSIS radar is a classic nadir‐looking altimeter, i.e. the current system configuration does not support acquisition in the SAR nor SARIn mode that CryoSat‐2 does, and former airborne radars (ASIRAS and KAREN) used in previous CryoVEx campaigns.
The processing is, although, performed with a form of along‐track SAR processing to narrow the beam in that direction. A drawback from subbanded processing to emulate the operating parameters of the ASIRAS and AltiKA instruments, is that the subsurface interface is brighter than the surface, which may lead to ambiguity in the determination of the surface location, whereas the full‐bandwidth data resolve both interfaces distinctly.
One of the conclusions in Rodríguez‐Morales et al. (2020) is to include lower frequency C/S‐band (2– 8 GHz) to fully utilize the capabilities to capture thin snow over sea ice. However, this would demand an alternative antenna setup for the DTU system, as there cannot be fitted a third antenna in the hole of the aircraft with the current setup.
Over the East Greenland Ice Sheet we obtained nearly identical results when comparing the ALS minus Ka‐band radar offsets along the survey line. The mean value of the elevation differences for both comparisons is close to zero, with a standard deviation of 0.71 m. This is what can be expected for summer conditions.
It was also found that the Ku‐band is capable of tracking a sub‐surface layer at an average depth of 30 cm (assuming the same dielectric constant of 1.53). This sub‐surface layer is not visible in the Ka‐band.
|Campaign name||Cryovex/ICESat-2 Summer 2019|
|Mission Instrument||ALS, Cresis radar|
|Field of Application||Sea and land ice. Radar and laser altimetry|
|Data Size||50 GB|
Digital Object Identifier: European Space Agency, 2022, CryoVEx/ICESat-2 Summer 2019 : https://doi.org/10.5270/ESA-b72e63c