General Questions

• What is AIRS?
• What does the AIRS instrument suite measure?
• What AIRS data products are available from GES DISC? Does the data cost anything?
• What is AIRS Algorithm Version versus Data Collection?
• What is the format of AIRS data products? Are conversion tools available?
• What is the daily volume of AIRS data products and the size of each granule?
• May I order data in smaller units than your granules (subsets of the granules)?
• What is the length of time between satellite measurement and data availability?
• Where do I go online to search and order AIRS data?

Documentation Questions

• Where can I find basic Readmes for AIRS data products?
• Where can I find complete users guides for AIRS data products and instruments?
• Where can I find information about the AIRS algorithms?
• Where can I find information about the 2378 AIRS IR channel properties?
• What document gives a description of the AIRS data field attributes (geolocation, swath)?
• What are the AIRS Earth Science Data Type (EDST) data collection descriptors?
• Where can I access disclaimers about AIRS data?
• From where can I get the current version of AIRS Level 2 retrieval algorithms?

Data Access Questions

• Who can order AIRS data products?
• Do I need to register to become a new user?
• Is AIRS data available via FTP to/from any site?
• Why would there be missing data for certain days?
• Who can I contact for help with ordering AIRS data?

AIRS Subsetting Questions

• What are the AIRS subset services at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC)?
• What is "Golden Set of Channels" offered for AIRS channel subsetting services?
• What are the channels contained in the "Numerical Weather Prediction Set"?

AIRS Imagery Questions

• Where can I get browse images of AIRS data? Do the images cost anything?
• What purpose do browse images serve?
• Why should I take time to preview an image?
• Can I use the browse image for research and analysis purposes?
• What is the volume of a browse image?

Science

• What is the repeat cycle for AIRS?
• What is the vertical resolution of AIRS Level-2 products?
• What is cloud-clearing method?
• Does AIRS Level-2 product include measurements from AMSU and HSB?
• Can radiance value be negative?
• Where can I find AIRS-RTA?
• Where can I find AIRS band chart?
• How can I find when AIRS over a particular area?

Answers to General Questions

 
• What is AIRS?

The Atmospheric Infrared Sounder (AIRS) is a facility instrument onboard the polar-orbiting Earth Observing System (EOS) Aqua satellite which was successfully launched on May 4, 2002. In combination with the Advanced Microwave Sounding Unit (AMSU-A) and the Humidity Sounder for Brazil (HSB), the AIRS instrument suite constitutes an innovative atmospheric sounding group of visible, infrared, and microwave sensors.

 
• What does the AIRS instrument suite measure?

The AIRS instrument is a high resolution spectrometer with 2378 bands in the thermal infrared spectral region (3.74 - 15.4 micrometers) and 4 bands in the visible spectral region (0.4 - 1.0 micrometers). These ranges have been specifically selected to determine atmospheric temperature with an accuracy of of 1 K per 1 km thick layer in the troposphere and moisture profiles at an accuracy of 20% per 2 km thick layer in the lower troposphere (20% 60% in the upper troposphere). See the AIRS instrument guide for details.

AMSU-A is a multi-channel microwave temperature/humidity sounder that measures global atmospheric temperature profiles and provides information on atmospheric water in all of its forms (with the exception of small ice particles, which are transparent at microwave frequencies). Information from AMSU-A in the presence of clouds is used to correct the AIRS infrared measurements for the effects of clouds. See the AMSU-A instrument guide for details.

HSB is primarily a humidity sounder providing supplementary water vapor and liquid data to be used in the cloud clearing process. Due to its higher spatial resolution (which equals that of AIRS) and a higher scan rate, the measurement density is 2.4 times that of AMSU-A. See the HSB instrument guide for details. The HSB instrument failed on February 5th, 2003.

 
• What AIRS data products are available from Goddard GES DISC? Does the data cost anything?

See AIRS Data Product page for the complete list of publicly available products. AIRS data is available to thepublic at NO COST.

• What is AIRS Algorithm Version versus Data Collection?

  Version 2.7 Algorithm produced Collection 1
  Version 3 Algorithm produced Collection 2
  Version 4 Algorithm produced Collection 3
  Version 5 Algorithm produces Collection 5
  
  Starting with the delivery of Algorithm Version 4 in 2005, AIRS Instrument Team began to produce two types of retrievals due to the failure of HSB on February 5, 2003. Data types that encompass retrievals using HSB data will have "H" letter in the short name of the data type, e.g. AIRH2RET.  Retrievals without HSB have the familar names, e.g. AIRX2RET. 
  
  Documentation is associated with the Version of the Algorithm, which is embedded in the data filenames.
  
  Data are organized and stored as Collections at GES DISC. Collections are different from the Algorithm Version until Version 5 where data version became the same as the collection. Our search engines will naturally show Collections.
  
  Because reprocessing earlier data takes time and multiple months are scheduled concurrently, Collections generated by the previous Algorithm Version will necessarily coexist for a period of time along with Collections generated by the current Algorithm Version. Users are cautioned to double-check the Collection before downloading to ensure the data are those desired.

 
• What is the format of AIRS data products? Are conversion tools available?

All AIRS data products are in HDF-EOS format. See our Tools page for details.

 
• What is the daily volume of AIRS L1B and L2 data products, and the size of each granule?

The daily volume of AIRS L1B products is:

• L1B-AIRS-IR-Rad: 13,440 Mb
• L1B-Vis/NIR-Rad: 2,640 Mb
• L1B-AMSU-Rad: 144 Mb
• L1B-HSB-Rad: 408 Mb
• L2-Standard-Product: 552 Mb
• L2-Support-Product: 2,496 Mb
• L2-Cloud-Cleared-Rad: 2,280 Mb

The average size of each granule:

• L1B-AIRS-IR-Rad: 56 Mb
• L1B-Vis/NIR-Rad: 11 Mb
• L1B-AMSU-Rad: 0.6 Mb
• L1B-HSB-Rad: 1.7 Mb
• L2-Standard-Product: 2.3 Mb
• L2-Support-Product: 10.4 Mb
• L2-Cloud-Cleared-Rad: 9.5 Mb
 
• May I order data in smaller units than your granules (subsets of the granules)?

Yes. When you order data from GES DISC, you can add on channel or variable subsetting options to be applied on L1B and L2 products.

 
• What is the length of time between satellite measurement and data availability?

There will typically be a 30-hour to 36-hour lag for AIRS L1B processed data.

 
• Where do I go online to search and order AIRS data?

There are several options available for obtaining AIRS data, see our Data Access page for a list of options. Because all the AIRS data are online, these data access methods will converge on the FTP step at the end. Pick one method that suits your preference.

Answers to Documentation Questions

 
• Where can I find basic Readmes for AIRS data products?

Our readmes contain brief information about data product characteristics, data ordering, read software and contact information. The readmes for AIRS data products are available at:
http://disc.sci.gsfc.nasa.gov/AIRS/documentation.shtml

 
• Where can I find complete users guides for AIRS data products and instruments?

These guides contain detailed information about data product characteristics, ordering, distribution, usage and instruments. The users guides for AIRS data products and instruments are available at: http://disc.sci.gsfc.nasa.gov/AIRS/documentation.shtml


 
• Where can I find information about the AIRS algorithms?
  
  The AIRS Algorithm Theoretical Basis Document is available at the EOS Project Science Office: http://eospso.gsfc.nasa.gov/eos_homepage/for_scientists/atbd/viewInstrument.php?instrument=2

 
• Where can I find information about the 2378 AIRS IR channel properties?

A channel-by-channel list which describes all 2378 of the AIRS IR channels can be found at: http://disc.sci.gsfc.nasa.gov/AIRS/documentation.shtml

 
• What document gives a description of the AIRS data field attributes (geolocation, swath)?

The document called AIRS Processing Files Description provides a detailed description of the dimensions, geolocation fields, full swath data fields and other attributes.

 
• What are the AIRS Earth Science Data Type (EDST) data collection descriptors?

AIRS ESDT collection descriptors contain all AIRS HDF-EOS metadata attributes (headers) such as version number, data date, spatial coordinates, etc. AIRS ESDTs as well as other platform instrument ESDTs can be found at: The EOS Core System (ECS) Information page: http://ecsinfo.gsfc.nasa.gov/ECSInfo/ecsmetadata/ESDT/ESDT_descriptors.html

 
• Where can I access disclaimers about AIRS data?

Disclaimers document is prepared by the AIRS science team and it can be found at:
http://disc.sci.gsfc.nasa.gov/AIRS/documentation.shtml

 
• From where can I get the current version of AIRS Level 2 retrieval algorithms?

The source code has not been cleared for public release at this time. The plan is to release the source code in the future, via Direct Broadcast contacts, but no schedule has been established for the release of Level 2 code. If you wish to compare retrieval products, the AIRS project is happy to cooperate and work with you as long as you choose to use actual AIRS data instead of simulation data.

Answers to Data Ordering Questions

 
• Who can order AIRS data products?

All NASA Earth Observing System (EOS) mission data including AIRS data is freely available to the public. Anyone can order these data products free of charge.

 
• Do I need to register to become a new user?

Registration is not required to obtain AIRS data from GES DISC. On the other hand, the AIRS science team at NASA JPL encourages you to register with them so that you will receive announcements of discovered features and caveats which are directly applicable to your area of research. You will also receive the AIRS Newsletter.

 

• Is AIRS data available via FTP to/from any site?

See our Data Access page for the server names and directory paths. You may also subscribe to the AIRS data so that the data products can be pushed to your site. Please contact User Services to set up FTP push.

 

 
• Why would there be missing data for certain days?

There are several possible reasons for missing data:


• The launch of the Aqua satellite that carries the AIRS instrument occurred on May 4, 2002. Processing on AIRS data to be distributed to the public began on data date March 12, 2003.
  
• If you are seeking most recent data, it is possible the data is still in the processing pipeline and will soon be available. There is typically a lag from the time instrument observations are made on the satellite until the data is processed and made available to the public.
  
• Sometimes satellite maneuvers, other necessary onboard procedures or technical problems will cause gaps in the data collection. Those instances will be documented and found at the NASA JPL AIRS website when appropriate.
 
• Who can I contact for help with ordering AIRS data?

If you need assistance with ordering via GES DISC or WIST, please contact the GES DISC User Service group at 301-614-5224 or send an email to help-disc@listserv.gsfc.nasa.gov

GES DISC User Services
NASA GSFC Code 610.2
Greenbelt, MD 20771
FAX (301) 614-5268

Answers to AIRS Subsetting Questions

 
• What are the AIRS subset services at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC)?
  
  When you order data through WHOM or Mirador search engine, you can choose variable or channel subsetting on AIRS L1B and L2 products. L3 subsetting can be done in Giovanni.
  

 

• What is "Golden Set of Channels" offered for AIRS channel subsetting services ?
  
  These are the groups of channels recommended by the AIRS Science Team for channel subsetting of AIRS L1B and L2 products. See table below. The grouping is generally based on hardware module in the AIRS instrument. The channel number range and the frequency range in addition to module name for each set are also listed to give a better description of each set. These are meant to make it easy for users to select all channels in various frequency ranges. The "comments" in this table are only meant as comments to let users know typical uses for data in this range. For example M-06 has the comment "Ozone". Not all channels in this set are necessarily good for ozone and not all ozone channels are in this set. It is the set of all channels on module 6, and the most prominent feature of this section of the spectrum is ozone sensitivity. One may also note that frequency ranges overlap somewhat between the modules, so frequency ranges can be deceptive.
  
  

Hardware Module	Frequency Range	Channel Number Range	Number of Channels	Comments
All	649.61 - 2665.24cm-1	1 - 2378	323	The Numerical Weather Prediction sets
M-12	649.61 - 681.99cm-1	1 - 130	130	Long-wave temperature sounding
M-11	687.60 - 728.44cm-1	131-274	143	Long-wave temperature sounding
M-10	728.06 - 781.88cm-1	275 - 441	166	Long-wave surface
M-09	789.26 - 852.43cm-1	442 - 608	166	Long-wave surface
M-08	851.49 - 903.78cm-1	609 - 769	160	Long-wave surface
M-07	911.24 - 974.29cm-1	770 - 936	166	Long-wave surface
M-06	973.82 - 1046.20cm-1	937 - 1103	166	Ozone
M-05	1056.10 - 1136.66cm-1	1104 - 1262	158	Long-wave surface, Ozone
M-04d	1216.97 - 1272.59cm-1	1263 - 1368	105	Water vapor
M-04c	1284.35 - 1338.86cm-1	1369 - 1462	93	Water vapor, methane
M-03	1338.16 - 1443.07cm-1	1463 - 1654	191	Water vapor
M-04b	1460.27 - 1527.00cm-1	1655 - 1760	105	Water vapor
M-04a	1541.10 - 1613.86cm-1	1761 - 1864	103	Water vapor
M-02b	2181.50 - 2325.06cm-1	1865 - 2014	149	Shortwave temperature sounding, CO
M-01b	2299.80 - 2422.85cm-1	2015 - 2144	129	Shortwave temperature sounding
M-02a	2446.20 - 2569.75cm-1	2145 - 2260	115	Shortwave Surface
M-01a	2541.90 - 2665.24cm-1	2261 - 2378	117	Shortwave Surface

• What are the channels contained in the "Numerical Weather Prediction (NWP) Set"?
  
  The NWP set is the set of channels used by Numerical Weather Prediction centers. These channels were selected as key well-behaved channels (as of 2003) that collectively have almost as much information as the full 2378 channel set.
  
  

Index	Channel Number	Frequency (wavenumber)
1	1	649.612976
2	6	650.807007
3	7	651.046021
4	10	651.765015
5	11	652.005005
6	15	652.968018
7	16	653.208984
8	17	653.450012
9	20	654.174988
10	21	654.416992
11	22	654.658997
12	24	655.143982
13	27	655.872986
14	28	656.116028
15	30	656.604004
16	36	658.070007
17	39	658.80603
18	40	659.052002
19	42	659.544006
20	51	661.767029
21	52	662.015015
22	54	662.512024
23	55	662.760986
24	56	663.008972
25	59	663.757019
26	62	664.507019
27	63	664.757019
28	68	666.010986
29	69	666.262024
30	71	666.765991
31	72	667.018005
32	73	667.27002
33	74	667.521973
34	75	667.775024
35	76	668.028015
36	77	668.281006
37	78	668.533997
38	79	668.786987
39	80	669.041016
40	82	669.549011
41	83	669.802979
42	84	670.057983
43	86	670.567017
44	92	672.099976
45	93	672.356995
46	98	673.640991
47	99	673.898987
48	101	674.414001
49	104	675.189026
50	105	675.447998
51	108	676.226013
52	110	676.744995
53	111	677.005005
54	113	677.526001
55	116	678.307983
56	117	678.570007
57	123	680.142029
58	124	680.403992
59	128	681.45697
60	129	681.721008
61	138	689.491028
62	139	689.762024
63	144	691.119019
64	145	691.390991
65	150	692.755005
66	151	693.028992
67	156	694.400024
68	157	694.674011
69	159	695.224976
70	162	696.052002
71	165	696.880981
72	168	697.711975
73	169	697.98999
74	170	698.267029
75	172	698.823975
76	173	699.10199
77	174	699.380981
78	175	699.659973
79	177	700.218018
80	179	700.776978
81	180	701.057007
82	182	701.617981
83	185	702.460999
84	186	702.742004
85	190	703.869995
86	192	704.435974
87	193	704.718994
88	198	706.137024
89	201	706.991028
90	204	707.846985
91	207	708.705994
92	210	709.565979
93	213	710.429016
94	215	711.005005
95	216	711.29303
96	218	711.870972
97	221	712.739014
98	224	713.609009
99	226	714.190979
100	227	714.481995
101	232	715.940979
102	239	717.994019
103	248	720.651001
104	250	721.244019
105	251	721.541016
106	252	721.838013
107	253	722.13501
108	256	723.028992
109	257	723.328003
110	261	724.523987
111	262	724.823975
112	267	726.325989
113	272	727.833984
114	295	734.150024
115	299	735.382019
116	300	735.690002
117	305	737.236023
118	308	738.166992
119	309	738.478027
120	310	738.789001
121	318	741.286011
122	321	742.22699
123	325	743.484985
124	333	746.013977
125	338	747.603027
126	355	753.057007
127	362	755.325012
128	375	759.573975
129	453	793.171021
130	475	801.098999
131	484	804.385986
132	497	809.179993
133	528	820.833984
134	587	843.913025
135	672	871.289001
136	787	917.30603
137	791	918.747009
138	843	937.90802
139	870	948.184021
140	914	965.43103
141	950	979.127991
142	1003	1001.38397
143	1012	1005.263
144	1019	1008.29999
145	1024	1010.48102
146	1030	1013.10901
147	1038	1016.63501
148	1048	1021.07703
149	1069	1030.52795
150	1079	1035.08899
151	1082	1036.46497
152	1083	1036.92395
153	1088	1039.22705
154	1090	1040.151
155	1092	1041.07703
156	1095	1042.46802
157	1104	1056.104
158	1111	1059.44397
159	1115	1061.36096
160	1116	1061.84094
161	1119	1063.28503
162	1120	1063.76697
163	1123	1065.21594
164	1130	1068.60999
165	1138	1072.51501
166	1142	1074.47803
167	1178	1092.45105
168	1199	1103.19897
169	1206	1106.82605
170	1221	1114.67505
171	1237	1123.16199
172	1252	1131.229
173	1260	1135.57495
174	1263	1216.974
175	1266	1218.49597
176	1278	1224.62305
177	1285	1228.22498
178	1290	1230.81104
179	1301	1236.53894
180	1304	1238.10999
181	1329	1251.35706
182	1371	1285.47498
183	1382	1291.70898
184	1400	1302.03699
185	1401	1302.61499
186	1402	1303.19397
187	1403	1303.77295
188	1415	1310.76599
189	1424	1316.05798
190	1449	1330.97595
191	1455	1334.60498
192	1466	1339.68701
193	1471	1342.23804
194	1477	1345.31201
195	1479	1346.34094
196	1488	1350.98804
197	1500	1357.23596
198	1519	1367.25305
199	1520	1367.78503
200	1538	1377.42603
201	1545	1381.21301
202	1565	1392.15295
203	1574	1397.13501
204	1583	1402.15295
205	1593	1407.77295
206	1614	1419.72595
207	1627	1427.229
208	1636	1432.47095
209	1644	1437.16394
210	1652	1441.88794
211	1669	1468.82703
212	1674	1471.91003
213	1681	1476.24695
214	1694	1484.36902
215	1708	1493.21497
216	1717	1498.95801
217	1723	1502.81006
218	1740	1513.83203
219	1748	1519.07397
220	1751	1521.04895
221	1756	1524.35205
222	1763	1542.44897
223	1766	1544.48206
224	1771	1547.88196
225	1777	1551.98096
226	1780	1554.03796
227	1783	1556.10095
228	1794	1563.70898
229	1800	1567.89001
230	1803	1569.98901
231	1806	1572.09204
232	1812	1576.31702
233	1826	1586.25903
234	1843	1598.495
235	1852	1605.04602
236	1865	2181.49512
237	1866	2182.3999
238	1867	2183.30688
239	1868	2184.21411
240	1869	2185.12207
241	1872	2187.8501
242	1873	2188.76099
243	1875	2190.58496
244	1876	2191.49805
245	1877	2192.41211
246	1881	2196.07495
247	1882	2196.99292
248	1883	2197.91089
249	1884	2198.83008
250	1897	2210.8479
251	1901	2214.57202
252	1911	2223.93604
253	1917	2229.59204
254	1918	2230.53711
255	1921	2233.37695
256	1923	2235.2749
257	1924	2236.2251
258	1928	2240.03296
259	1937	2248.64795
260	1938	2249.60889
261	1939	2250.57104
262	1941	2252.49707
263	1946	2257.3269
264	1947	2258.29492
265	1948	2259.26392
266	1958	2269.00098
267	1971	2281.78101
268	1973	2283.75903
269	1988	2298.70508
270	1995	2305.7439
271	2084	2363.98389
272	2085	2364.94092
273	2097	2376.48999
274	2098	2377.45801
275	2099	2378.42603
276	2100	2379.39502
277	2101	2380.36499
278	2103	2382.30811
279	2104	2383.28003
280	2106	2385.22705
281	2107	2386.2019
282	2108	2387.17798
283	2109	2388.15405
284	2110	2389.13208
285	2111	2390.11011
286	2112	2391.08911
287	2113	2392.06812
288	2114	2393.04907
289	2115	2394.03003
290	2116	2395.01196
291	2117	2395.99512
292	2118	2396.979
293	2119	2397.96411
294	2120	2398.94897
295	2121	2399.93604
296	2122	2400.9231
297	2123	2401.91089
298	2128	2406.86304
299	2134	2412.83203
300	2141	2419.83496
301	2145	2446.19507
302	2149	2450.2981
303	2153	2454.41406
304	2164	2465.80396
305	2189	2492.0791
306	2197	2500.60205
307	2209	2513.49292
308	2226	2531.97803
309	2234	2540.76904
310	2280	2561.12891
311	2318	2600.49902
312	2321	2603.65991
313	2325	2607.88696
314	2328	2611.06592
315	2333	2616.38306
316	2339	2622.79199
317	2348	2632.46606
318	2353	2637.87207
319	2355	2640.04102
320	2363	2648.75195
321	2370	2656.4231
322	2371	2657.52197
323	2377	2664.13794

Answers to AIRS Imagery Questions

 
• Where can I get browse images of AIRS data? Do the images cost anything?

AIRS Daily summary browse images can be viewed through AIRS summary browse search option in GES DAAC Search and Order. The AIRS summary browse data is used as only ordering tool and cannot be distributed to public users as a data product. Starting from Version 5, the summary browse images are discontinued.

All browse images SHOULD NOT be used as the basis of any science research and do not constitute a research-quality product. The images are available at NO COST.

 
• What purpose do browse images serve?

Browse images are low-resolution visualizations used in search and order tools. The purpose of having browse images is to allow science data users to get an idea about what is in the data before ordering the data. For example, users should be able to tell if a location they have selected is sufficiently cloud-free or cloudy enough for cloud studies. In other words, the browse images have a role in helping users to select and organize the science data they have obtained.

 
• Why should I take time to preview an image?

In the GES DISC Search and Order interface (WHOM or Mirador), there is an option to preview a data granule before ordering the data granule. Previewing an image of the data can help to determine the extent and location of cloud cover, confirm its geographical location, or observe quality problems such as speckling, line drops, and sun glint. However, this is not to be confused with our AIRS summary browse image which is a daily product (i.e., some anomalies may not be visible on a summary browse image due to the sub-sampling process).

 
• Can I use the browse image for research and analysis purposes?

No. Browse images represent only a fraction of the original data or have a low-resolution. They should not be used for analysis, evaluation or interpretation of data content.

 
• What is the volume of a browse image?

The size of the browse images for L1B products are less than 200 kilobytes with most ranging from 100 to 150 kilobytes.

Answer to Science Questions

 
• What is the repeat cycle of AIRS?

The AIRS swath repeat cycle is 16 days.

 
• What is the vertical resolution of AIRS Level-2 products?

Standard product is on 28 pressure levels and Support product is on 100 pressure levels. Complete lists of those levels can be found at http://disc.sci.gsfc.nasa.gov/AIRS/documentation.shtml, under Level-2 Products section (Pressure Arrays). The documentation on AIRS Levels and Layers is also useful and can be found at the same web location.


 
• What is cloud-clearing method?

The cloud-clearing approach is used to retrieve atmospheric and surface properties. It relies on the fact that cloud amount tends to vary appreciably among nearby 15 km AIRS footprints, but that other atmospheric and cloud properties (averaged within AIRS footprints) are more uniform. This means that radiance differences between adjacent AIRS footprints are primarily caused by changes in cloud amount. Adjacent, multi-spectral observations can then be solved in a least squares sense for the infrared radiance that is common to the clear portions of all field of view. Since the effect of clouds has been removed, atmospheric and surface variables can be retrieved from these radiances as if no clouds were present. Cloud properties can be also determined based on the difference between observed and cloud-cleared radiances.

In this technique, any aerosols that interact with IR radiation can be treated as an unusual cloud layer. As with water clouds, there must be a clear region somewhere within each AMSU-A footprint. Thus, narrow smoke plumes are not a problem, but a uniform dust layer extending more than 45 km across would get folded into the "clear-column" radiances and could degrade the atmospheric retrieval. To assess the impact of such horizontally widespread aerosols, it should be noted that stratospheric sulfuric acid aerosols are optically thin in the IR, except after large volcanic eruptions. Tropospheric anthropogenic aerosols are also optically thin to AIRS because of their small size.

Although this method has been used and proved by existing systems (TOVS), it should be noticed that the higher spectral resolution of AIRS allows this technique to be exploited to a higher degree than ever before.

 
• Does AIRS Level-2 product include measurements from AMSU and HSB?

One flavor of the AIRS Level-2 Standard and Support Products does. Their product names are AIRH2RET and AIRH2SUP respectively. The end date for these products is 2003-Feb-05 due to HSB instrument failure. The Standard Product (AIRX2RET) and Support Product (AIRX2SUP) are careated using only the AIRS and AMSU, without HSB.

 
• Can radiance value be negative?

In general, AIRS can have negative radiances for shortwave channels. When the scene temperature is low, below 200K, shortwave AIRS channels can have negative radiances. This happens over very high cloud in tropics and over Antartica.

In bad channels, radiance can be negative for several different reasons:

1) -9999.0 is used as a flag value when input data is missing or out of range. Out of range data happens most frequently as a result of sun glint causing saturation.
2) Radiances can go negative when the noise is greater than the scene. This will happen in very noisy detectors (so users should check the channel properties file and/or the ExcludedChans field in the data. Note ExcludedChans is not defined correctly in the docs. Any channel with a value 3 or higher should be ignored. NeN is also a good diagnostic of channels experiencing transient high noise episodes.)

The users should be warned to use only the channels that are marked good ( BadFlag = 0 in the channel property file.).

 
• Where can I find AIRS-RTA?

You can find AIRS-RTA in AIRS Level-2 ATBD,

http://eospso.gsfc.nasa.gov/eos_homepage/for_scientists/atbd/docs/AIRS/atbd-airs-L2.pdf

Section 4.2 Radiative Transfer of the Atmospheric in the Infrared.

 
• Where can I find AIRS band chart?

AIRS band chart can be found in AIRS channel properties files: http://disc.sci.gsfc.nasa.gov/AIRS/documentation.shtml under Level-1B Products section.

 
• How can I find when AIRS is over a particular area?

Various maps of the orbital tracks of Aqua (the satellite carrying AIRS) are available from University of Wisconsin's web site:

http://www.ssec.wisc.edu/datacenter/aqua/