CDDIS Bulletin - April 2001
Volume 16 No. 3

• Articles:
  • Format for Publication of the CDDIS Bulletin
  • High-Rate SolarMax IGS/GPS Campaign "HIRAC/SolarMax"
  • Archive of High-Rate GPS Data
• Data Bits and Bytes:
  • Permanent GPS and GLONASS Network Update

Format for Publication of the CDDIS Bulletin

This, the April 2001 issue of the CDDIS Bulletin, marks a change in the format of the publication to a fully electronic one. With the wide availability of the web, the CDDIS staff has realized that it is no longer necessary, or cost-effective, to publish a hardcopy version of the CDDIS Bulletin. We will, however, continue to publish information about the CDDIS and its data holdings through this electronic version of the bulletin. We hope that the user community continues to find this information interesting and useful to their research. Comments are, of course, welcome on our new format and on the contents of the publication in general.

High-Rate SolarMax IGS/GPS Campaign "HIRAC/SolarMax"

Joachim Feltens/ESOC, Norbert Jakowski/DLR Neustrelitz, Carey Noll/CDDIS

This year, the sun has reached the solar maximum and thus many interesting ionospheric phenomena at the polar caps and in the equatorial region can be observed.

For the first time during a solar maximum we have an opportunity to observe ionospheric behavior with the dense IGS GPS ground station network. Ionosphere scientists are thus very interested in the dual-frequency GPS (and GLONASS) tracking data collected from the IGS sites. Since many phenomena in the ionosphere are short-lived (e.g., traveling wave structures) and cannot be extracted with the standard thirty-second sampling rate of the "classic" IGS RINEX files, there is much interest to collect high-rate GPS tracking data, e.g. with a one or three-second sampling rate, during a dedicated IGS campaign. The current solar maximum is a unique chance to establish such a high-rate tracking database which could be the subject of ionospheric analyses over the years. The IGS sponsored a similar campaign during the solar eclipse on August 11, 1999 (see the August and October 1999 issues of the CDDIS Bulletin).

This IGS activity supporting the solar maximum was coordinated with other ionospheric observation programs or measurement campaigns using ionosondes, EISCAT, high resolution magnetometers, etc. to obtain a comprehensive view of the geomagnetic and ionospheric state. There are two regions of major interest:

1. the polar regions and
2. low latitudes including the crest regions at both sides of the geomagnetic equator.

As chairman of the IGS Ionosphere Working Group, Joachim Feltens has proposed, together with Dr. Norbert Jakowski from DLR Neustrelitz, to organize a dedicated IGS tracking campaign. The duration of the campaign was seven days, April 23 through 29, 2001. Initially, the campaign was to end on Friday, April 27; a request was issued by Dr. Feltens to continue the observations through Sunday due to a large solar flare whose impact was felt on the Earth through the weekend.

As with the 1999 Solar Eclipse campaign, the CDDIS has agreed to provide an archive of the GPS and GLONASS data contributed to this campaign. The data are available through anonymous ftp to host cddisa.gsfc.nasa.gov in the filesystem /gps/01solarmax/yyddd/yyt, where yy is the two-digit year, ddd is the three-digit day of year, and t is the file type (d, g, m, n, o, s).

A list of the stations (PS or PDF) and map (GIF or PDF) which proposed to participate in the GPS/GLONASS tracking campaign is available. This list and map will be updated periodically as data are received and archived at the CDDIS.

Questions about the campaign can be directed to Dr. Joachim Feltens and/or Dr. Norbert Jakowski; questions about data access can be directed to the CDDIS Manager, Carey Noll.

Archive of High-Rate GPS Data

In 1999, the IGS issued a Call for Participation in the Low Earth Orbiters (LEO) Pilot Project. The goal of the project is to explore the role of LEO missions in the IGS, identifying possible activities for the IGS and its components in spaceborne GPS missions. This activity will start this summer. The CDDIS proposed to serve as a data center for the pilot project and in this capacity will retrieve, reformat, archive and provide access to data from a ground network of forty to fifty low-latency GPS receivers operating at a one-second sampling rate. The CDDIS will also archive data from GPS flight receivers on board the CHAMP and SAC-C satellites. Analysts can retrieve these data to produce precise orbits of the LEO platforms, which will aid in the generation of other products, such as temperature and water vapor profiles in the neutral atmosphere and ionosphere imaging products. The LEO Pilot Project will test the ability of the various components of the IGS infrastructure to support near real-time acquisition, dissemination, and processing of GPS data.

Activity has begun at the CDDIS to support the pilot project. JPL is now supplying one-second data from a network of seventeen stations shown in Table 1. The files are available at:

ftp://cddisa.gsfc.nasa.gov/pub/gps/hrdata/yyddd/hh

where yy is year, ddd is day of year, hh is hour (00-23).

Filenames are of the form ssssdddhmm.yyt.Z where ssss is the four-character monument name, ddd is the day of year, h is the hour (a-x), mm is the minute (00, 15, 30, 45), yy is the year, and t is the file type (d for Hatanaka-compressed RINEX observation data and n for navigation data).

Table 1. GPS Stations Supplying High-Rate Data to the CDDIS

It is expected that additional sites from other operational data centers (e.g., NRCan, GFZ, etc.) will be archived at the CDDIS within the next few weeks. Furthermore, GPS data from receivers onboard SAC-C and/or CHAMP will also be archived. A revised, enhanced version of RINEX, Version 2.20, has been developed to accommodate the data from flight receivers.

DATA BITS AND BYTES

This section is designed to give brief notices of special events, new data sets, or problems encountered in recent months. The CDDIS staff believes the user community should be informed of these problems in order to ensure that the best results possible are produced from data issued by the archive.

Permanent GPS and GLONASS Network Update

Since the January 2001 issue of the CDDIS Bulletin, the CDDIS has archived daily and hourly GPS (Table 2) and daily GLONASS (Table 3) data from the following new tracking sites:

Table 2. New GPS Daily and Hourly Tracking Sites

Notes: An * in the above table denotes daily sites previously archived at the CDDIS that have just recently started to provide hourly and/or meteorological data.

Table 3. New GLONASS Tracking Sites

Notes: An * in the above table denotes daily sites previously archived at the CDDIS that have just recently started to provide hourly and/or meteorological data.