Swedish Institute of Space Physics

June 18, 1997

Dr. R. B. Sheldon
Center for Space Physics
Boston University
725 Commonwealth Ave
Boston MA 02215 USA

Dear Colleagues,

We enjoyed looking at the nice ENA images obtained by the IPS/ POLAR instrument and reading your paper "First energetic neutral atom images from Polar" in the May 15 issue of Geophysical Research Letters, pages 1167-1170. ENA imaging receives more and more credits from the magnetophseric community and the POLAR results are and will be contributing to this new and exciting area.

Besides the POLAR spacecraft, two more satellites GEOTAIL and the Astrid microsatellite, have recently performed ENA measurements. While the GEOTAIL results have been partially referenced in your paper, the Astrid measurements have not been mentioned at all, despite the fact that they have been reported at many conferences including all the AGU meetings since the fall 1995. The papers presenting the Astrid ENA data were initially submitted for publication in Geophysical Research Letters on February 21, 1996 but the referees considered them as "having no direct scientific interest" and stated that the results were too qualitative since the global ion flux reconstruction had not been performed. We found this criticism unfair and the reports biased by non-scientific matters and we, thus, refused to publish our results in GRL. The papers have recently been accepted for publication in Advances in Space Research. We enclose copies for your attention.

We are glad that your work did not suffer from the scepticism towards ENA imaging, as our Astrid reports did, and that new important results became quickly available for the scientific community. We are looking forward to seeing further reports on POLAR findings in the area of ENA imaging.

Yours sincerely,

Prof. Rickard Lundin
Dr. Stas Barabash
Mr. Pontus C:son Brandt

Enc: Copies of two Papers:
Energetic Neutral Atom Imaging by the Astrid Microsatellite
ENA Imaging from the Swedish Micro Satellite Astrid During the Magnetic Storm of 8 February, 1995.

Cc: Dr. M. G. Henderson
Dr. G. D. Reeves
Dr. H. E. Spence
Dr. R. B. Sheldon
Dr. A. M. Jorgensen,
Dr. J. B. Blake
Dr. J. F. Fennell