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The Solar-Terrestrial Physics Division of the National Geophysical Data Center (NGDC) wishes to announce the permanent closure of the Maui, Hawaii, ionosonde site on June 1, 1994. The site has run for more than 50 years with an amazing record of reliability thanks, in the last 16 years, to Stephen S. Barnes' mindful efforts to keep the vintage C2 film-based ionosonde running smoothly. The historical archive of ionograms held at NGDC for Maui will remain an invaluable resource. Its closure will leave a large hole in Pacific Ocean and in global coverage of ionospheric vertical incidence data.



Last year I was asked what effect the closure of the South African ionosonde network would have on IPS. This is a general issue affecting many groups and I feel the ideas I presented may have wider interest. For instance, it is often hard to think what to put in such a letter. It is also hard to see that it is really any of your business, even when the request for support is clearly personal. I am offering this letter as a sample letter I sent supporting a particular ionosonde network. If you have written a similar letter of support recently, please consider having a copy published in INAG. The ideas in these letters may be helpful for others seeking to express their support, but uncomfortable with the style and content that will most effectively in stating their beliefs.


Here is what I wrote.


You pose a difficult question - what can I say to persuade you to continue to operate your ionosonde network? It is an expensive activity and if you are not getting value from the network yourself then why should you be making the effort on behalf of people elsewhere? There is no simple answer to this but it is a question that is being posed by many other people.


First, it is as well to establish some important issues regarding the operation of an ionosonde network. The longer, and more reliably a network has been operated, the more important and the more easily replaced it becomes. A paradox? We (at IPS) find that because the South African network has been reliable in the past, the monthly maps of the F2 region that we have prepared for the globe are well defined in the region of South Africa. For simple, but important work of this type, the past contribution from your stations will always be preserved for general purpose use. This is true for many other good ionosonde stations around the world. Many could have closed ten years ago and we would still benefit today from their past existence. However, we can make that observation only with hindsight. To make it with any certainty, we need reliable stations to continue to operate for as long as their institutes can afford to support them. Reliable station networks are fundamentally important to the global ionosonde network as a whole because their reliability acts as a standard against which apparent secular changes can be measured. In other words, the longer a network has collected data, the more desirable it is for it to continue to collect data. I have written in the INAG Bulletin on the topic of baseline stations. I believe this is a valuable function and an excellent reason for maintaining long term ionosonde networks.


With this background, I will answer your questions.


How is the data that we receive used? Some years ago, all data received at IPS were promptly entered into the computer and compared against our global ionospheric maps. This is still a relevant exercise, but we have limited people available, and far more for them all to do, so it is not done as regularly as was once the case. However, over a period of two to three years, all the monthly median data we receive are still entered in the computer and used as a check on our global ionospheric maps. In addition, they are also used to calculate an ionospheric index. The sooner we receive the data, the more impact these data have on our regular operations. On occasions, we are involved in studies of the ionosphere where hourly data becomes important. The recent series of Sundial campaigns is an example. During these periods, we entered hourly data and studied stations in comparison with each other to build a global picture of ionospheric storms and disturbances. South African data is most important in these studies as there is almost no other comparable information in the world. This is partly because of the Atlantic anomaly, partly the paucity of data in the southern hemisphere. These type of studies are carried out irregularly, but I always use the South African data when I do this type of work. There have been occasions when an ionospheric storm is seen in Australia, but not in South Africa, and on another occasion, there was a storm in Europe, but nowhere else. The South African data established that nothing was seen in comparable southern locations. Unfortunately, this work was not published. It was part of a larger study that has, recently, suffered funding setbacks.


What would be the impact if the data were discontinued? It would produce an important global gap in our knowledge of the ionosphere. When event analyses are carried out, the southern hemisphere will be poorly represented. In your time sector there is only one station reporting data outside South Africa - that is the French station at La Reunion. It is far enough north of your stations to leave your geographical and geomagnetic region unmeasured. The significance of this can be measured against the general comments I have made above. In the longer term, as we move towards global ionospheric mapping, as I feel we will, your region will not be covered. There is no other reliable mid latitude ionospheric information available.


At IPS, and also through INAG, we are exploring ways to make the data recorded at ionosonde stations useful in real time. There appear to be a growing number of potential applications for real time data. I feel that where possible, these options should be harnessed first as support for established stations and second as a basis for establishing new stations. To some extent this will depend on how significant HF is in your region. I can quote examples, for instance, Pakistan has invested in three ionosondes to cover all of their country. Other groups are moving in similar directions. Single site direction finding systems require ionosonde data for real time updates. IPS is exploring ways that such systems can use our ionosonde stations in real time. While there appears to be an interest, there is also, still, a major problem getting the data from a station to the person who can use them in a timely fashion. While this could be solved now, it appears a difficult task that will be easily managed in the near future rather than now. We feel that this approach is necessary if large numbers of ionosonde stations are to be supported in the future. IPS also feel that networks will need to become digital based and use computer scaling software for real time data. This is a reasonable financial investment for a network that is having problems, but it should be a small investment compared to the capital outlay over past years.


I hope these comments are some help. I recognise that eventually funding becomes an important problem and it is not possible to continue to support a network. We are aware that our own future is by no means guaranteed even though ionospheric sounding has a reasonable profile in Australia. If people do not see an immediate need it is very difficult to sustain their interest. I will be publishing an INAG Bulletin in May and if you wish to put in a note outlining your situation and ask for further input, I will be happy to include the note. I should add, however, that it is difficult to get people to commit any thoughts to paper in regard to station closures. Please don't interpret a lack of response as a lack of interest. I agree the silence is no help to you, but people don't always recognise their responsibilities in these matters. They may think, as happened in IPS once, that by saying the data are useful they are placing you under an obligation to supply them.


That is what I said. It is longer than necessary and did not result in the continued routine collection of ionosonde data in South Africa, as is apparent from the URSI INAG Meeting report.


It is very important that we work together, share our ideas on these matters and become a more effective voice supporting our ionosonde networks, both in our own country and in others. I would be very pleased, as I have said, to publish similar letters of support for ionosondes and for groups involved in ionospheric research. I feel we can all benefit from an exchange of ideas in this area.

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