Typhoon Sinlaku weakened to a tropical storm by September 19, 2008 as it continued along Japan’s east coast. Sinlaku is the name of a goddess worshipped on the island of Kosrae in Micronesia, according to the Hong Kong Observatory, which lists tropical cyclone names in use in the Pacific. Photo Credit: NASA JPL
Kendra Cook
C2 International
703-652-4809 begin_of_the_skype_highlightingåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊ703-652-4809åÊåÊåÊåÊåÊåÊend_of_the_skype_highlighting begin_of_the_skype_highlightingåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊåÊ703-652-4809åÊåÊåÊåÊåÊåÊend_of_the_skype_highlighting / kcook@c2iconsulting.com
Peter Wilczynski
NOAA/NESDIS
301-807-3524 / Peter.Wilczynski@noaa.gov
Background
COSMIC is a joint U.S.-Taiwan 6-microsatellite demonstration mission that was launched in April 2006 and is being operated by Taiwan’s National Space Organization (NSPO). Its mission is to demonstrate the value of near-real-time Global Positioning System Radio Occultation (GPS-RO) data to global users. GPS-RO is a technique where the transmitters on GPS satellites and GPS receivers on low Earth orbiting (LEO) satellites (for example, COSMIC) are located on the opposite sides of the planetary limb. Orbital motion of one or both instruments produces the limb scanning geometry. The technique provides a unique combination of high precision and vertical resolution at long wavelengths that penetrate through the atmosphere in nearly all conditions. Figure 1 illustrates a COSMIC satellite in LEO intercepting the GPS signal in order to perform GPS-RO.
COSMIC is the world’s first operational GPS-RO mission for global Earth weather forecasting and climate monitoring. The data have also been valuable for atmospheric, ionospheric, and geodetic research. The National Oceanic and Atmospheric Administration (NOAA) has been providing ground station services for the mission from two locations in the U.S. and one in Norway since April 2008. The satellite system is currently operating with high reliability and providing global data in near-real-time to over 1,000 users worldwide, including NOAA.
The GPS-RO data have been demonstrated to be valuable to the climate, meteorology, and space weather communities. These communities include both users of real-time forecasts, as well as U.S. and international research communities. The COSMIC data have been shown to increase the accuracy of the predictions of hurricane behavior, significantly improve long-range weather forecasts, and monitor climate change with unprecedented accuracy. An example of the increase in weather forecast accuracy is the Ensemble Forecasts of Typhoon Sinlaku in 2008. The following figure illustrates the typhoon forecast with and without COSMIC data.
Figure 1. COSMIC Satellite Intercepting GPS Signals (1)
The red line is the observed track of the typhoon, the black lines are the forecasts of each of the forecasting ensemble members, and the green line is the ensemble mean. As illustrated in Figure 1, the leftward-turning tendency of the typhoon track is predicted significantly better with the assimilation of COSMIC data.
Unfortunately, the COSMIC mission will reach the end of its design life in 2011, and the critical real-time satellite observing capability will begin to degrade with fewer operational satellites. It is expected that these spacecraft will begin to degrade in the 2011 timeframe, with the loss of 2-3 spacecraft between 2011 and 2015. In February 2008, NOAA’s Under Secretary of Commerce for Oceans and Atmosphere stated in his FY10ÛÒFY14 Program Decision Memorandum that the NOAA Satellite Mission Sub-goal was to ÛÏdevelop a follow-on plan for the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC).Û As a result, NOAA intends to provide data continuity and improve sensing capability with the next-generation COSMIC-2.
COSMIC-2 Objectives
The objective of COSMIC-2 is similar to that of COSMIC: to collect a large amount of atmospheric data for meteorological, climatic, ionospheric, and geodetic research, as well as for weather forecasting and space weather monitoring. Additionally the system will allow scientists to collect data over un-manned and remote regions (such as the poles and oceans) in support of research in these areas.
COSMIC-2 will meet its objective by intercepting signals from not only the U.S. GPS, but also the European satellite system GALILEO, and the Russian Global Navigation Satellite System (GLONASS) with a satellite-based receiver and inferring the deviations in each signal’s straight-line path caused by temperature and moisture gradients, as shown in Figure 1. This is known as GNSS-RO since it is utilizing more global navigation satellite signals than just the U.S. GPS signals.
Figure 2. Ensemble Forecasts of Typhoon Sinlaku With and Without COSMIC Data (1), (2)
COSMIC-2 Constellation and Mission
COSMIC-2 is expected to be a much improved system consisting of a new constellation of 12 satellites for an operational mission. The mission payload will be a TriG GNSS-RO (Global Navigation Satellite System-Radio Occultation) receiver and will collect more data points per receiver by adding the capability to track the GALILEO and GLONASS systems, which will produce a significantly higher spatial and temporal density of profiles over tracking GPS signals alone. This additional information should significantly improve weather prediction models and severe weather forecasting (including typhoons and hurricane forecasting), as well as benefit related research in the fields of meteorology, ionosphere and climate. In addition to the mission payload, discussions are underway regarding the feasibility of hosting several secondary science / technology payloads.
The constellation is planned to be composed of 6 satellites at 72 degree inclination, and 6 satellites at 24 degree inclination, which will enhance observations in the equatorial region over what is currently being collected with COSMIC.
This constellation will produce more than 8,000 soundings per day, compared to the approximate 2,000 soundings per day currently produced by COSMIC due to COSMIC-2’s ability to track three navigation systems’ signals versus COSMIC’s ability to track one. Figure 4 illustrates the comparison of sounding distribution over a three hour period between COSMIC and COSMIC-2.
Figure 4. COSMIC vs. COSMIC-2 Sounding Comparison (1)
The first COSMIC-2 launch is planned for the second quarter of FY14. Initial Operational Capability (IOC) of COSMIC-2 is expected to be in the third quarter of FY14, and Final Operational Capability (FOC) is targeted for early FY17. Similar to the current COSMIC satellites, the COSMIC-2 satellites are nominally expected to be 50-60kg each, and therefore several can be launched on one small rocket ÛÒ in the class of Minotaur 1, Falcon 1E or Pegasus. The plan is to launch two rockets with 6 satellites on each rocket. They will be launched and then positioned into their final orbits (nominally 800km altitude) [3].
COSMIC-2 Architecture
The current COSMIC mission allows one data downlink per orbit. The plan for COSMIC-2 is to allow for 2 data downlinks per orbit, which will considerably reduce the data latency. Consequently, COSMIC-2 will require more satellite ground stations for receiving the data. As with COSMIC, the data collected by COSMIC-2 will be downlinked to the tracking station, then transmitted to the COSMIC processing center (CDAAC in Boulder, CO) as well as to the Taiwan processing center (TACC) for processing. The processed products will then be provided to NOAA Global Transmission System (GTS) for distribution to the worldwide weather prediction centers. Command and Control for the COSMIC-2 constellation will continue to be provided by the NSPO Satellite Operations Control Center (SOCC). Payload operational configurations will continue to be managed by a joint effort between UCAR (University Corporation for Atmospheric Research) and JPL (Jet Propulsion Laboratory) with NOAA and NSPO concurrence for updates and changes [3].
The following figure depicts the overall COSMIC-2 System Architecture.
Figure 5. COSMIC-2 System Architecture (4)
COSMIC-2 is a joint mission, and as such, NOAA shall be responsible for [3]:
Û¢ acquisition and management of the mission payload, which is a GNSS-RO payload;
Û¢ overall management of the data analysis, application, and distribution segment;
Û¢ acquisition and management of the launch vehicle system;
Û¢ acquisition and management of the ground receiving stations;
Û¢ acquisition and management of the data processing centers in the U.S.
NSPO shall be responsible for [3]:
Û¢ acquisition, management, and deployment of satellites constellation;
Û¢ development and management of mission operation;
Û¢ modification and operations of Satellite Operations Command and Control (SOCC)
station and Taiwan’s Telemetry, Tracking & Command station;
Û¢ acquisition and management of Taiwan data processing center.
NOAA and NSPO shall be jointly responsible for [3]:
Û¢ acquisition and management of the scientific payloads.
Current Status Of COSMIC-2
The U.S.-Taiwan agreement that authorizes the COSMIC-2 program was signed by both parties in May 2010. The Joint Program Office held the Feasibility Design Review (FDR) in May 2010 and completed the Mission Definition Review (MDR) in August 2010. System Requirements Review (SRR) is scheduled for April 2011, the Preliminary Design Review (PDR) in October 2011, and the Critical Design Review (CDR) in June 2012.
NSPO officially sent out a Request for Information (RFI) in July 2010 and five spacecraft vendors have submitted spacecraft designs to NSPO for COSMIC-2. NSPO is anticipating releasing a Request for Proposal (RFP) in early 2011 and is planning on completing their spacecraft selection process by April 2011.
Conclusion
COSMIC’s contribution to weather prediction is considered to be ÛÏsignificantÛ by the National Weather Service (NWS) and represents an immense benefit to worldwide forecasting capability. This data is not available globally from other sources, and allowing this data to deteriorate due to the COSMIC satellites’ end-of-life will result in a significant diminution of performance of the NOAA Numerical Weather Models. This will result in diminished weather prediction capability which may lead to increased costs and loss of life due to natural disasters. The realization of COSMIC-2 will continue to fulfill this important mission and further increase weather forecast capabilities.
References
[1] Courtesy of UCAR (University Corporation for Atmospheric Research, Boulder, CO) [2] Courtesy of CWB (Taiwan’s Central Weather Bureau) [3] COSMIC-2 Joint Management Control Plan [4] Courtesy of NSPO (Taiwan’s National Space Organization) [5] GPS Radio Occultation (RO) Technique (Kursinski et al., 1995)