ULYSSES
SOLAR CORONA EXPERIMENT (SCE)

The Ulysses dual-frequency radio subsystem was utilized by the Ulysses Solar Corona Experiment (SCE) to measure the electron content (column density) and its variations during the first solar conjunction (C1) of the Ulysses mission in the summer of 1991 and the fourth solar conjunction (C4) in the winter of 1995. In the nominal mode for radio-sounding observations [Bird et al., 1992a], both downlinks (S-band: f_s = 2.3 GHz; X-band: f_x = 8.4 GHz) are phase coherent with the uplink (S-band: f_u = 2.1 GHz). The dual-frequency radio-sounding technique exploits the dispersive nature of ionized media on the propagation of the two downlinks. The tiny Doppler shift due to plasma moving in and out of the ray path is greater at S-band than at the higher frequency X-band. Similarly, because the group velocity of waves propagating in ionized media is smaller for lower frequencies, the round-trip time of propagation for coded range signals between the spacecraft and the ground station will be longer at S-band than at X-band.

SCE Data Types

The SCE data are obtained from the Radio Science Support group at JPL [Asmar and Renzetti, 1993; Asmar et al., 1995]. There are basically two types of data: Ranging and Doppler (Frequency), recorded at the tracking sites of the NASA Deep Space Network (DSN) as a function of UT Ground Received Time [DSN810-5]. The raw data are delivered in special binary files called ATDFs (Archival Tracking Data Files), containing Ranging and Doppler data from the standard DSN tracking receivers. There are high time resolution Doppler data from special radio science receivers (so-called 'open loop' data) as well. These are in files called ODRs (Original Data Records). ATDFs are files of radiometric data produced by the Network Operations Control Center (NOCC) Navigation Subsystem (NAV). They are derived from Intermediate Data Records by NAV and contain all radiometric measurements received from the DSN station including signal levels (`AGC' = automatic gain control in dBm), antenna pointing angles, frequency (often referred to simply as `Doppler'), range, and residuals. Doppler data are often used to infer spacecraft radial motion relative to the tracking antenna. Data values in ATDFs are reported at rates no higher than 10 per second. For the Ulysses solar conjunction C1 the received frequencies at S-Band and X-band were recorded at a nominal sample time of one per second. Ranging data were recorded nominally at intervals of ca. 10 minutes. Each ATDF data record contains 117 parameters, stored in records of 288 bytes. The ATDF is described in section TRK-2-25 of the JPL Document 820-13 [DSN 820-13].

SCE Data Recording Opportunities

The ranging data from the ATDFs have been analyzed for the solar conjunction C1 and a number of publications describe the results [Pätzold et al., 1992; Bird et al., 1994; Woo et al., 1995a; Woo et al., 1995b; Pätzold et al., 1997]. Ranging results from the geometrically unique fourth Ulysses solar conjunction (C4) are also available [Pätzold et al., 1995; Bird et al., 1996; Pätzold and Bird, 1998]. Coronal velocities as a function of solar distance were derived from the C1 Doppler data using a correlation technique between uplink and downlink [Wohlmuth et al., 1997]. Differences in the spectral characteristics of electron density fluctuations observed in coronal holes vs. corona streamers were reported from analyses of the C4 Doppler data [Pätzold et al., 1996; Karl et al., 1997].

The Ulysses spacecraft was occulted by the Io Plasma Torus (IPT) during its Jupiter encounter on 8 February 1992. The Ulysses radio subsystem was utilized to measure the columnar electron density of the IPT on this occasion [Bird et al., 1992b; 1993]. These data, together with all Ulysses results from the Jupiter encounter, are archived at the Planetary Data System (PDS).

SCE Data Processing

Ranging Data

Data files have been generated which contain the ranging data at an advanced stage of processing. After stripping the ranging data from the ATDFs and weeding out obviously bad data, tables of the measured data plus physically relevant quantities were produced for the archive as function of time.

Ranging data during the Ulysses solar conjunctions C1 (7 August to 5 September 1991) and C4 (23 February to 14 March 1995) have been provided to this archive in the RANGE_C1.TXT and RANGE_C4.TXT files. As an example, the first few lines of RANGE_C1.TXT are as follows:

year mo dd hh:mm:ss set no dss difrng econt
1991- 8- 7T 1:11:23.712Z 1 1 43 557 2227
1991- 8- 7T 1:21:24.192Z 1 2 43 555 2219
1991- 8- 7T 1:31:24.672Z 1 3 43 567 2267
1991- 8- 7T 1:41:24.288Z 1 4 43 575 2299
1991- 8- 7T 1:51:23.904Z 1 5 43 578 2311
1991- 8- 7T 2: 1:23.520Z 1 6 43 574 2295
1991- 8- 7T 2:11:24.000Z 1 7 43 567 2267
1991- 8- 7T 2:21:23.616Z 1 8 43 575 2299
1991- 8- 7T 2:31:23.232Z 1 9 43 584 2335
1991- 8- 7T 2:41:23.712Z 1 10 43 570 2279
1991- 8- 7T 2:51:24.192Z 1 11 43 572 2287
1991- 8- 7T 3: 1:24.672Z 1 12 43 582 2327
1991- 8- 7T 3:11:24.288Z 1 13 43 591 2363
1991- 8- 7T 3:31:23.520Z 1 14 43 596 2383
1991- 8- 7T 3:41:24.000Z 1 15 43 588 2351



where:

year = 1991 or 1995
mo = month of year
dd = day of month
hh:mm:ss = hours, minutes seconds (UT, ground received)
set = running no. for each DSN tracking pass during C1/C4
no = running no. for range measurement within each tracking pass
dss = DSN station number
difrng = differential range delay in `range units' (RU) [DSN 810-5]
econt = electron content in `hexems' [Bird et al., 1992a; 1994]

Note: difrng (RU) and econt (hexems) are given to the nearest respective unit. The estimated accuracy of a differential range measurement is of the order of 50 range units.

The following table gives an idea about the size and coverage of the Ranging data set from solar conjunctions C1 and C4 and the Jupiter encounter:

Ulysses SCE Ranging Data:

SCE start stop ascii size gzip size
Event mo:dd:hh:mm mo:dd:hh:mm (kB) (kB)
C1 : 1991 08:07:01:11 09:05:17:55 88 20
Jup : 1992 02:05::21:44 09:02:18:44 22 4
C4 : 1995 02:23:05:06 03:14:14:06 145 33

Doppler Data

Data files have been generated from the ATDFs which contain the quantities of interest for analysis of the Ulysses downlink frequencies. The data set for the first solar conjunction C1 in 1991 from DOY 218-248 (6 August to 5 September) consists of the following files : 
DOP91218.063.gz  DOP91227.012.gz  DOP91235.043.gz  DOP91242.014.gz
DOP91219.043.gz  DOP91227.043.gz  DOP91235.063.gz  DOP91242.043.gz
DOP91219.061.gz  DOP91227.063.gz  DOP91236.014.gz  DOP91243.014.gz
DOP91220.043.gz  DOP91228.014.gz  DOP91236.043.gz  DOP91243.063.gz
DOP91221.014.gz  DOP91228.063.gz  DOP91237.014.gz  DOP91244.014.gz
DOP91221.043.gz  DOP91229.014.gz  DOP91237.063.gz  DOP91244.063.gz
DOP91221.143.gz  DOP91229.043.gz  DOP91238.014.gz  DOP91245.014.gz
DOP91222.014.gz  DOP91229.063.gz  DOP91238.043.gz  DOP91245.063.gz
DOP91222.043.gz  DOP91230.014.gz  DOP91238.063.gz  DOP91246.014.gz
DOP91223.014.gz  DOP91230.063.gz  DOP91239.014.gz  DOP91246.043.gz
DOP91223.043.gz  DOP91231.014.gz  DOP91239.043.gz  DOP91247.014.gz
DOP91224.014.gz  DOP91231.063.gz  DOP91239.063.gz  DOP91248.014.gz
DOP91224.063.gz  DOP91232.014.gz  DOP91240.014.gz  DOP91248.043.gz
DOP91225.014.gz  DOP91233.014.gz  DOP91240.063.gz  datalist.c1
DOP91225.063.gz  DOP91234.014.gz  DOP91241.012.gz
DOP91226.014.gz  DOP91234.043.gz  DOP91241.043.gz
DOP91226.063.gz  DOP91234.063.gz  DOP91241.063.gz
The data set for the fourth solar conjunction C4 in 1995 from DOY 53-73 (22 February to 14 March) consists of the following files : 
DOP95053.042.gz  DOP95057.042.gz  DOP95063.042.gz  DOP95069.012.gz
DOP95054.012.gz  DOP95057.061.gz  DOP95063.061.gz  DOP95069.042.gz
DOP95054.061.gz  DOP95057.142.gz  DOP95064.061.gz  DOP95069.061.gz
DOP95054.161.gz  DOP95057.161.gz  DOP95065.042.gz  DOP95070.042.gz
DOP95055.042.gz  DOP95058.061.gz  DOP95065.061.gz  DOP95070.061.gz
DOP95055.061.gz  DOP95059.042.gz  DOP95065.142.gz  DOP95071.012.gz
DOP95055.142.gz  DOP95059.061.gz  DOP95066.042.gz  DOP95071.042.gz
DOP95055.161.gz  DOP95060.042.gz  DOP95066.061.gz  DOP95071.061.gz
DOP95056.012.gz  DOP95060.061.gz  DOP95067.012.gz  DOP95072.042.gz
DOP95056.042.gz  DOP95061.012.gz  DOP95067.042.gz  DOP95072.061.gz
DOP95056.061.gz  DOP95061.042.gz  DOP95067.061.gz  DOP95073.042.gz
DOP95056.161.gz  DOP95062.042.gz  DOP95068.012.gz  DOP95073.061.gz
DOP95057.012.gz  DOP95062.061.gz  DOP95068.042.gz  datalist_c4.txt
The "gz" suffix means that these files have been compressed with the UNIX gzip utility. They can be expanded to ascii tables with the analog gunzip utility. Each file contains dual-frequency Doppler data at a sample rate of 1 point per second from each tracking pass. The filename provides the day-of-year (doy) and ground tracking station (dss) according to the scheme "DOPyydoy.dss", where the year number is yy = 91 (C1) or 95 (C4). The doy given to each file applies to the start of the data recording. The deep space stations of the NASA Deep Space Network (DSN) used for SCE are:

DSS 12 Goldstone 34-m
DSS 14 Goldstone 70-m
DSS 42 Canberra 34-m
DSS 43 Canberra 70-m
DSS 61 Madrid 34-m
DSS 63 Madrid 70-m

Some tracking passes, especially at the Canberra stations, continue on into the next doy. Normally, a "0" preceeds the dss number. The few cases with a "1" rather than "0" are a separate tracking pass at the same dss later on the same doy. The files "datalist_c1.txt" and "datalist_c4.txt" contain listings of each tracking pass with such information as date, ATDF number, start and end times of pass, start and end times of data recording, pass duration, station overlaps, etc. Each file contains 15 columns per data point defined as follows:

column explanation
1-4 : time tag (UT, ground received)
1 : DOY in 1991 (C1) or 1995 (C4)
2 : HH
3 : MM
4 : SS
5 : DSS
6 : uplink frequency [Hz]
7-10 : S-band receiver parameters
7 : agc [dBm]
8 : downlink frequency [Hz]
9 : downlink frequency residual [Hz]
10 : total slipped cycles during count
11-14 : X-band receiver parameters
11 : agc [dBm]
12 : downlink frequency [Hz]
13 : downlink frequency residual [Hz]
14 : total slipped cycles during count
15 : differential Doppler from Counts

A more detailed explanation of the parameters is given in section TRK-2-15 of the JPL Document 820-13 [DSN820-13].

The total volume of validated SCE Doppler data from both solar conjunctions submitted to the archives is given in the following table.

conjunction phase # passes # hours total # hours overlap size-ASCII (MB) size-gzip (MB)
C1-ingress 30 169.4 12.2 74.0 14.9
C1-egress 34 201.0 14.4 87.8 17.5
C1-total 64 370.4 26.6 161.8 32.4
C4-ingress 27 188.2 5.1 73.8 14.8
C4-egress 24 194.0 7.5 76.0 15.2
C4-total 51 382.2 12.6 149.8 30.0
C1+C4 115 752.6 39.2 311.6 62.4



The SCE Doppler data from the Io Plasma Torus occultation during Jupiter encounter, available here online, are archived using a different format. The size of the data set has been reduced by providing only the Doppler data from the tracking passes at DSS 43/42 on Jupiter encounter day, when the spacecraft was occulted by the Io Plasma Torus on 1992 DOY 39 from 11:00 to 20:45 (ground received time).

time (hrs) S-band phase S-3/11X AGC
10.99999992 1566823818.441 -0.075 -150.9
11.00027784 1567875175.345 -0.071 -150.9
11.00055552 1568926527.281 -0.067 -151.3
11.00083344 1569977874.261 -0.043 -151.1
11.00111112 1571029216.279 -0.054 -151.6
11.00138880 1572080553.284 -0.090 -151.3
11.00166672 1573131885.437 0.010 -151.6

where

time (hours) = time in hours on 8 FEB 1992 (DOY 39)
S-Band phase = running S-band Doppler count (cycles)
S-3/11X = differential frequency (Hz)
AGC = S-band received signal level (dBm)

An additional complication is the compensation for the Earth's ionosphere to separate its contribution from that of the Io Plasma Torus. This requires obtaining ionospheric calibration data from the DSN for the days of the Jupiter encounter. Details of the calibration procedure can be found in section TRK-2-23 of JPL document 820-13 [DSN820-13]. The necessary parameters for the ionospheric calibration during the above DSN tracking pass are:

tstart=10.25000; tstop=21.41667 and

c_0=0.7528; c_1=-2.5346; c_2=5.6032; c_3=3.4620; c_4=-1.4765; c_5=-2.5889

with

tstart = start time for the interval of ionospheric calibration
tstop = stop time for the interval of ionospheric calibration
c_i, i=0,5 = polynomial coefficients for ionospheric calibration

References

Asmar, S.W., R.G. Herrera, and T. Priest, Radio Science Handbook , JPL D-7938 Volume 6, Jet Propulsion Laboratory, Pasadena, CA, 1995.

Asmar, S.W., and N.A. Renzetti, The Deep Space Network as an Instrument for Radio Science Research , Jet Propulsion Laboratory Publication 80-93, Rev. 1, 15 April 1993.

Bird, M.K., S.W. Asmar, J.P. Brenkle, P. Edenhofer, M. Pätzold, and H. Volland, The coronal-sounding experiment, Astron. Astrophys. Supp. Ser. 92, 425-430, 1992a.

Bird, M.K., S.W. Asmar, J.P. Brenkle, P. Edenhofer, O. Funke, M. Pätzold and H. Volland, Ulysses radio occultation observations of the Io plasma torus during the Jupiter encounter, Science 257, 1531-1535, 1992b.

Bird, M.K., S.W. Asmar, P. Edenhofer, O. Funke, M. Pätzold and H. Volland, The structure of Jupiter's Io plasma torus inferred from Ulysses radio occultation observations, Planet. Space Sci. 41, 999-1010, 1993.

Bird, M.K., H. Volland, M. Pätzold, P. Edenhofer, S,W, Asmar and J.P. Brenkle, The coronal electron density distribution determined from dual-frequency ranging measurements during the 1991 solar conjunction of the Ulysses spacecraft, Astrophys. J. 426, 373-381, 1994.

Bird, M.K., M. Pätzold, P. Edenhofer, S.W. Asmar and T.P. McElrath, Coronal radio sounding with Ulysses: Solar wind electron denity near 0.1 AU during the 1995 conjunction, Astron. Astrophys. 316, 441-448, 1996.

DSN 810-5: Deep Space Network / Flight Project Interface Design Book , Document 810-5, Jet Propulsion Laboratory, Pasadena, CA.

DSN 820-13: Deep Space Network System Requirements / Detailed Interface Design , Document 820-13, Jet Propulsion Laboratory, Pasadena, CA.

Karl, J., M. Pätzold and M.K. Bird, Coronal radio sounding: Non-Gaussian turbulence in the source regions of slow and fast solar wind, Geophys. Res. Lett. 24, 2881-2884, 1997.

Pätzold, M., and M.K. Bird, Polar plumes and fine-scale coronal structures - On the interpretation of coronal radio sounding data, Geophys. Res. Lett. 25, 1845-1848, 1998.

Pätzold, M., M.K. Bird, H. Volland, P. Edenhofer, S.W. Asmar, and J.P.
Brenkle, Coronal sounding with Ulysses: Preliminary results from the first solar conjunction, in Solar Wind Seven, E. Marsch and R. Schwenn (eds.), Pergamon Press, Oxford, 237-240, 1992.

Pätzold, M., M.K. Bird, P. Edenhofer, S.W. Asmar and T.P. McElrath, Dual-frequency radio sounding of the solar corona during the 1995 conjunction of the Ulysses spacecraft, Geophys. Res. Lett. 22, 3313-3316, 1995.

Pätzold, M., J. Karl and M.K. Bird, Coronal radio sounding with Ulysses: Dual-frequency phase scintillation spectra in coronal holes and streamers, Astron. Astrophys. 316, 449-456, 1996a.

Pätzold, M., B.T. Tsurutani and M.K. Bird, An estimate of large-scale solar wind density and velocity profiles in a coronal hole and the coronal streamer belt, J. Geophys. Res. 102, 24,151-24,160, 1997.

Wohlmuth, R., D. Plettemeier, P. Edenhofer, M.K. Bird, M. Pätzold and S.W. Asmar, Measurement of the propagation speed of plasma inhomogenieties in the solar corona using an uplink/downlink correlation method, Radio Sci. 32, 617-628, 1997.

Woo, R., J.W. Armstrong, M.K. Bird and M. Pätzold, Variation of fractional electron density fluctuations inside 40 solar radii observed by Ulysses ranging measurements, Geophys. Res. Lett. 22, 329-332, 1995a.

Woo, R., J.W. Armstrong, M.K. Bird and M. Pätzold, Fine-scale filamentary structure in coronal streamers, Astrophys. J. 449, L91-L94, 1995b.

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