Ground-based HF to VHF radar calibration by scattering off a stratospheric balloon

Renkwitz, Toralf; Clahsen, Matthias; Latteck, Ralph

doi:10.5194/amt-19-1825-2026

Articles | Volume 19, issue 5

https://doi.org/10.5194/amt-19-1825-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-19-1825-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 19, issue 5

Research article

|

12 Mar 2026

Research article |

| 12 Mar 2026

Ground-based HF to VHF radar calibration by scattering off a stratospheric balloon

Toralf Renkwitz, Matthias Clahsen, and Ralph Latteck

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Final revised paper (published on 12 Mar 2026)
Preprint (discussion started on 02 Dec 2025)

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-5722', Anonymous Referee #1, 05 Feb 2026

The manuscript is well written and clearly organized, which facilitates comprehension of the proposed methodology. It presents an interesting and innovative technique for the calibration and inter-comparison of different operational radars by exploiting the scattering characteristics of a stratospheric balloon. Although the underlying analysis can be technically demanding, the authors describe the technique in sufficient detail, allowing the reader to understand the approach and assess its applicability and robustness.
Section 2.1 MAARSY radar. Please include the frequency of the radar

Citation: https://doi.org/10.5194/egusphere-2025-5722-RC1
- AC1: 'Reply on RC1', Toralf Renkwitz, 06 Feb 2026
  
  We thank the reviewer #1 for his help in evaluating our manuscript.
  
  Curiously we indeed missed to clearly stated the operating frequency of MAARSY. Instead we only mentioned it in the general description of the range covered by all the radar system involved in this study.
  
  We will add this information at the introduction of MAARSY.
  
  Citation: https://doi.org/10.5194/egusphere-2025-5722-AC1
RC2:
'Comment on egusphere-2025-5722', Anonymous Referee #2, 05 Feb 2026

I found the manuscript very interesting and the technical content to be of high quality and suitable for publication. I suggest the authors make a copy-editing pass over the manuscript before publication. Some examples that could be improved are as follows:
6. even more -> especially

16. these … are -> this … is

35 northnorwegian

66: CassiopeiaA -> Cassiopeia A

100: 96.3° then eq. 1 93.7°?

Fig 8: colorbar label missing (currently located in title string). 8 hexagons? Perhaps 8 antenna groups?

287: “maximum AoA coverage by SIMONe (≈ 150 km), Saura (≈ 120 km) and MAARSY (≈ 40 km) was

accomplished.” Would it make sense to express this coverage also in angular units? i.e. how far off Zenith can each radar provide accurate AoA?

Citation: https://doi.org/10.5194/egusphere-2025-5722-RC2
- AC2: 'Reply on RC2', Toralf Renkwitz, 06 Feb 2026
  
  The evaluation of the submitted manuscript is very appreciated.
  We agree on the lingual deficits and adapted to the suggestions, and thank for finding them.
  >96.3° then eq. 1 93.7°?
  
  Unfortunately, this was phrased too vaguely. What was meant here, is that one is the measured mean phase-offset between the antennas within the array, while the equation represents a free-space approximation. However, the two values do not differ greatly. We rephrase it accordingly.
  >Fig 8: colorbar label missing (currently located in title string). 8 hexagons? Perhaps 8 antenna groups?
  Correct, we didn't add a label to the colorbar in Figures 7-9 yet, but marked it in the figure titles, we will add the labels to the colorbars.
  
  The term "hexagons" is actually related to our internal name of the smallest subarray groups and it has been used as such in earlier publications, but only after a proper introduction. We correct the term for: "hexagon-shaped subarray groups".
  
  >287: “maximum AoA coverage by SIMONe (≈ 150 km), Saura (≈ 120 km) and MAARSY (≈ 40 km) was accomplished.” Would it make sense to express this coverage also in angular units? i.e. how far off Zenith can each radar provide accurate AoA?
  We agree, the given distances are likely confusing and will add the corresponding zenith angles for each distance.
  
  Citation: https://doi.org/10.5194/egusphere-2025-5722-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

AR by Toralf Renkwitz on behalf of the Authors (18 Feb 2026) Author's response Author's tracked changes Manuscript

ED: Publish as is (25 Feb 2026) by Marco Milla

AR by Toralf Renkwitz on behalf of the Authors (27 Feb 2026) Manuscript

Short summary

We describe the use of a nearby drifting stratospheric balloon to calibrate three different radar systems. While for radars in the VHF range different calibration options exist, it is much more complicate to do this in the lower HF range. The main complication is the required distance and size of the target, which is especially challenging for vertical pointing radars. We also present the validation of proper phase calibration and the general radiation pattern.