TGO Ramfjordmoen Ionosonde Data January 1991

About this dataset: This dataset contains ionograms in PNG format and covers data from January 01-31, 1991.About the Tromsø Ionosonde (1984-1992): During the period 1984-1992 the Ionosonde was situated at 69° 35' N, 19° 13' E at Ramfjordmoen near Tromsø, Norway and operated by the Auroral Observatory of the University of Tromsø. The instrument operated at this location prior to 1984, and still operates there (as of 2018); see the related publication for details. The instrument was fully digitized and based on a Hewlett Packard 21MX computer. The combination of a low power transmitter and complementary code transmission made the Tromsø ionosonde equivalent to a conventional ionosonde (at the time) with 20 µs pulses and 16 kW peak power. Routine operation was one ionogram every 20 min with a frequency sweep from 1 MHz to 12 MHz lasting between 2 and 3 min. For the 100 km altitude region the precision of determining the height of a sporadic E layer is ± 3 km. The ionograms were stored on magnetic tape. A noise discrimination routine in the computer program reduced the stored data to less than 10% of the raw data. In this way one 2400' tape held about 1300 ionograms, equivalent to 18 days' data. The tapes were 4-11 years old when they were read, resulting in around 20% data-loss during the process of transferring to other media. Today, storage is on online disk and with offline an archive on a variety of media.

本数据集说明：本数据集包含PNG格式的电离图（ionogram），涵盖1991年1月1日至31日的观测数据。
关于特罗姆瑟电离测高仪（Tromsø Ionosonde，1984-1992年）：1984至1992年间，该电离测高仪坐落于挪威特罗姆瑟附近的拉姆峡湾（Ramfjordmoen），地理坐标为北纬69°35′、东经19°13′，由特罗姆瑟大学极光观测台负责运行维护。该仪器早在1984年之前便已在此处运行，且截至2018年仍持续工作；详细信息可参阅相关学术出版物。该仪器已实现全数字化，以惠普（Hewlett Packard）21MX计算机作为核心控制系统。其搭配低功率发射机与互补编码传输技术的方案，使这款特罗姆瑟电离测高仪的性能等效于彼时配备20微秒脉冲、峰值功率16千瓦的传统电离测高仪。常规运行模式下，每20分钟采集一幅电离图，扫描频率范围为1兆赫至12兆赫，单次扫描耗时2至3分钟。在100千米高度区间内，该仪器对偶发E层（sporadic E layer）高度的测定精度为±3千米。所有原始电离图数据均存储于磁带上。计算机程序内置的噪声甄别算法可将存储数据压缩至原始数据量的10%以下。以此计算，一盘长度为2400英尺的磁带可存储约1300幅电离图，等效于18天的观测数据量。这批磁带在被读取时已有4至11年的存放时长，因此在向其他存储介质迁移的过程中出现了约20%的数据丢失情况。如今，该数据集采用在线磁盘与离线多介质归档相结合的方式进行存储。